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Easy Sequences 36: Hyperbolic Lattice Points

The graph, shown below, of the hyperbola: , passes through four positive lattice points:. ...

4 meses ago

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Easy Sequences 34: Modified Pascal's Triangle

Consider the integer triangle below: It follows the same ...

4 meses ago

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Easy Sequences 22: Sum of Proper Fractions

Let 'F' be the set of all proper fractions in lowest term, whose denominator is less than or equal 'd'. So, for d = 10, we have:...

4 meses ago

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Easy Sequences 28: Sum of Radicals of Integers

The radical of a positive integer is defined as the product of the distinct prime numbers dividing . For example, the distinct ...

4 meses ago

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Easy Sequences 29: Odd proper divisors of odd proper divisors

The number is special. It has odd number of proper divisors: . Furthermore, if you take any of its proper divisors, say , it t...

4 meses ago

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Easy Sequences 33: Web Trapped Ant

An ant is trapped on a spider web inside a can with open top. The can has a radius and height . A spider sitting on the outside...

4 meses ago

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List modest numbers up to n

After determining the nude numbers, or the numbers that openly display some of their divisors as their digits, one would think t...

4 meses ago

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Easy Sequences 21: Combinatorial Summations

Create the function S(n), defined by the following summation: The symbol is the combination f...

4 meses ago

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Easy Sequences 31: N-N's Sequence

We define the N-N's Sequence, as the series of all positive integers in ascending order and with repetition, wherein a appears ...

4 meses ago

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Easy Sequences 25: Product of Series

The function 'P(n)' is defined as the series product: where 'T(n)' is the triangular sum: ...

4 meses ago

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Easy Sequences 23: Hat Guessing Game!

Consider the following Game Show: Hats, with numbers written on each, were placed on the heads of the participants. Participant...

4 meses ago

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Multiply binary numbers

Write a function to multiply two binary numbers input as strings. For example, input values of ‘1011’ and ‘101’ should give ’110...

4 meses ago

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Count the primes in Collatz sequences

Several Cody problems (21, 69, 42937, 44448, 44784, 52422) involve Collatz sequences. These start with a seed . If is odd, the ...

5 meses ago

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List the Moran numbers

The quotient of a Moran number and its digit sum is prime. For example, 117 and 481 are Moran numbers because 117/(1+1+7) is 13 ...

5 meses ago

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Easy Sequences 6: Coefficient sums of derivatives

Consider the polynomial function and its first-order derivative . The sums of the coefficients of P and P', are and , respecti...

5 meses ago

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Determine whether a number is a fibodiv number

The number 14 is a fibodiv number because you can divide it into 1 and 4, use those numbers as the seeds for a Fibonacci sequenc...

5 meses ago

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Determine whether a number is unprimeable

The number 204 is unprimeable because no single digit can be changed to make it prime. In contrast, the number 207 is not unprim...

5 meses ago

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Count the ways to draw non-intersecting chords between points on a circle

There are 9 ways to draw non-intersecting chords between four points on the perimeter of a circle (including no chords at all). ...

5 meses ago

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Find the nth nude number

The number 672 is a nude number because it openly displays three of its divisors: 6, 7, and 2. In other words, a nude number is ...

5 meses ago

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Easy Sequences 9: Faithful Pairs

A "faithful number" is a non-prime number that is one less or one more than some prime number but not both. For example, for num...

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Easy Sequences 10: Sum of Cumsums of Fibonacci Sequence

The function F(n) is defined as the set of Fibonacci numbers from the first up to the n-th. S(n) is the result of applying to F,...

5 meses ago

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Easy Sequences 8: Triangles with integer sides and prime perimeters

The triangle below is special. It has integer sides and a prime perimeter. Given an integer "n" we want to know how many t...

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Hoax Numbers

A Hoax Number (OEIS A019506) is defined as a composite number, whose sum of digits is equal to the sum of digits of its distinct...

5 meses ago

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Easy Sequences 3: Prime 44-number Squares

The positive integers 62 and 238 are related. Their squares (3844 and 56,644) both end in '44'. In fact, 62 and 238 are the 3rd ...

6 meses ago

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Easy Sequences 2: Trigonometric function with integral input and output

The function 'F', defined as: , will always return an integer if the input is a natural number (in radian...

6 meses ago

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Double Fibonacci

double_fibonacci takes two integers, each greater than one, as input arguments (it does not have to check the format of the inpu...

6 meses ago

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Sort Except Zeros

Sort the numbers in a vector. But the position of zeros should not be changed. Example: sort_except_zeros( [5 3 0 0 2 4] ) == [...

6 meses ago

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Which Prime

Given two prime numbers, specify the relation between them i.e. - 'Twin Prime', 'Cousin Prime', 'Sexy Prime' or 'None'

7 meses ago

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Bessel Polynomials

Return the n-th Bessel polynomial Assume that n is a non-negative finite integer. bessel_poly(0) ans = 1 bessel_poly(1) ...

7 meses ago

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List Honaker primes

The number 131 is the 32nd prime number. It is a Honaker prime because the sum of its digits (1+3+1) equals the sum of the digit...

7 meses ago