OEIS sequence #A008566, deals with the following series:
This sequence is the digits of powers of 5 listed side by side, that is:
.
Given a digit d and index n, write a function , that outputs how many times d appears in the sequence segment .
For example, it is clear from the list above that, , and .
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HINT: OEIS did not provide a close formula for finding the elements of sequence #A008566. However, this sequence is not without a pattern. For example: except for , the last digit of is always 5, except for , the second last digit of is always 2, except for , the third last digit of is always either 1 or 6, etc... You may need this pattern as the use of big integer class is not required in this problem.
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Last Solution submitted on Jul 21, 2026

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William Chris Cleveland David Hill Ramon Villamangca

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