{"group":{"id":1,"name":"Community","lockable":false,"created_at":"2012-01-18T18:02:15.000Z","updated_at":"2026-05-26T00:16:20.000Z","description":"Problems submitted by members of the MATLAB Central community.","is_default":true,"created_by":161519,"badge_id":null,"featured":false,"trending":false,"solution_count_in_trending_period":0,"trending_last_calculated":"2026-05-26T00:00:00.000Z","image_id":null,"published":true,"community_created":false,"status_id":2,"is_default_group_for_player":false,"deleted_by":null,"deleted_at":null,"restored_by":null,"restored_at":null,"description_opc":null,"description_html":null,"published_at":null},"problems":[{"id":45189,"title":"Double Factorial","description":"Return double factorial\r\n\r\n        n(n-2)...(5)(3)(1),   n\u003e0, odd\r\nn!!  =  n(n-2)...(6)(4)(2),   n\u003e0, even\r\n        1                 ,   n = -1, or n = 0\r\n\r\nFor example\r\n\r\n6!! = (6)(4)(2) = 48","description_html":"\u003cp\u003eReturn double factorial\u003c/p\u003e\u003cpre\u003e        n(n-2)...(5)(3)(1),   n\u0026gt;0, odd\r\nn!!  =  n(n-2)...(6)(4)(2),   n\u0026gt;0, even\r\n        1                 ,   n = -1, or n = 0\u003c/pre\u003e\u003cp\u003eFor example\u003c/p\u003e\u003cp\u003e6!! = (6)(4)(2) = 48\u003c/p\u003e","function_template":"function y = doubleFactorial(x)\r\n  y = x;\r\nend","test_suite":"\r\ncorrectList = [1 1 2 3 8 15 48 105 384 945 3840 10395 46080 135135 645120 2027025 10321920];\r\nfor idx = 1:17\r\nassert(isequal(doubleFactorial(idx-1),correctList(idx)))\r\nend","published":true,"deleted":false,"likes_count":2,"comments_count":1,"created_by":8703,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":69,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2019-11-01T18:08:07.000Z","updated_at":"2026-05-30T02:33:35.000Z","published_at":"2019-11-01T18:08:34.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eReturn double factorial\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[        n(n-2)...(5)(3)(1),   n\u003e0, odd\\nn!!  =  n(n-2)...(6)(4)(2),   n\u003e0, even\\n        1                 ,   n = -1, or n = 0]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eFor example\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e6!! = (6)(4)(2) = 48\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"}],"problem_search":{"problems":[{"id":45189,"title":"Double Factorial","description":"Return double factorial\r\n\r\n        n(n-2)...(5)(3)(1),   n\u003e0, odd\r\nn!!  =  n(n-2)...(6)(4)(2),   n\u003e0, even\r\n        1                 ,   n = -1, or n = 0\r\n\r\nFor example\r\n\r\n6!! = (6)(4)(2) = 48","description_html":"\u003cp\u003eReturn double factorial\u003c/p\u003e\u003cpre\u003e        n(n-2)...(5)(3)(1),   n\u0026gt;0, odd\r\nn!!  =  n(n-2)...(6)(4)(2),   n\u0026gt;0, even\r\n        1                 ,   n = -1, or n = 0\u003c/pre\u003e\u003cp\u003eFor example\u003c/p\u003e\u003cp\u003e6!! = (6)(4)(2) = 48\u003c/p\u003e","function_template":"function y = doubleFactorial(x)\r\n  y = x;\r\nend","test_suite":"\r\ncorrectList = [1 1 2 3 8 15 48 105 384 945 3840 10395 46080 135135 645120 2027025 10321920];\r\nfor idx = 1:17\r\nassert(isequal(doubleFactorial(idx-1),correctList(idx)))\r\nend","published":true,"deleted":false,"likes_count":2,"comments_count":1,"created_by":8703,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":69,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2019-11-01T18:08:07.000Z","updated_at":"2026-05-30T02:33:35.000Z","published_at":"2019-11-01T18:08:34.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eReturn double factorial\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[        n(n-2)...(5)(3)(1),   n\u003e0, odd\\nn!!  =  n(n-2)...(6)(4)(2),   n\u003e0, even\\n        1                 ,   n = -1, or n = 0]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eFor example\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e6!! = (6)(4)(2) = 48\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"}],"errors":[],"facets":[[],[{"value":"easy","count":1,"selected":false}]],"term":"tag:\"double factorial\"","page":1,"per_page":50,"sort":"map(difficulty_value,0,0,999) asc"}}