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Sophie Germain prime
In number theory, a prime number p is a *Sophie Germain prime* if 2p + 1 is also prime. For example, 23 is a Sophie Germain prim...

2 months ago

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Circular Primes (based on Project Euler, problem 35)
The number, 197, is called a circular prime because all rotations of the digits: 197, 971, and 719, are themselves prime. The...

2 months ago

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Make a vector of prime numbers
Input(n) - length of vector with prime numbers Output(v) - vector of prime numbers Example: * n=1; v=2 * n=3; v=[2 3 5...

2 months ago

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Find the sum of the elements in the "second" diagonal
Find the sum of the elements in the diagonal that starts at the top-right corner and ends at the bottom-left corner.

2 months ago

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Divisible by n, Composite Divisors
Pursuant to <http://www.mathworks.com/matlabcentral/cody/problems/42453-divisible-by-n-prime-vs-composite-divisors Divisible by ...

2 months ago

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Divisible by n, prime divisors from 20 to 200
Pursuant to the previous problem (linked below), this problem requires a function that checks for divisibility of large numbers ...

2 months ago

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Divisible by n, Truncated-number Divisors
Some divisors only require a few numbers at the end of the number in question to determine divisibility, no matter how long. Exa...

2 months ago

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Divisible by n, prime divisors - 11, 13, 17, & 19
Divisibility checks against prime numbers can all be accomplished with the same routine, applied recursively, consisting of add ...

2 months ago

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Divisible by 13
Write a function to determine if a number is divisible by 13. Similar to the number seven, this can be done by a few different m...

2 months ago

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Divisors for big integer
Inspired by Problem 1025 and Project Euler 12. Given n, return the number y of integers that divide N. For example, with ...

3 months ago

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Sum of big primes without primes
Inspired by Project Euler n°10 (I am quite obviously a fan). With problem n°250 by Doug, you can find some global methods to co...

3 months ago

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Numbers spiral diagonals (Part 1)
Inspired by Project Euler n°28 et 58. A n x n spiral matrix is obtained by starting with the number 1 and moving to the right...

3 months ago

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Find the next Fibonacci number
In the sequence of Fibonacci numbers, every number is the sum of the two preceding ones: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55...

3 months ago

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Number of Even Elements in Fibonacci Sequence
Find how many even Fibonacci numbers are available in the first d numbers. Consider the following first 14 numbers 1 1 2...

3 months ago

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Project Euler: Problem 9, Pythagorean numbers
A Pythagorean triplet is a set of three natural numbers, a b c, for which, a^2 + b^2 = c^2 For example, 3^2 + 4^2 = 9 + 16 ...

3 months ago

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Project Euler: Problem 4, Palindromic numbers
A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 ...

3 months ago

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Project Euler: Problem 8, Find largest product in a large string of numbers
Find the greatest product of five consecutive digits in an n-digit number. 73167176531330624919225119674426574742355349194934...

3 months ago

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Project Euler: Problem 5, Smallest multiple
2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder. What is the smalle...

3 months ago

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Project Euler: Problem 1, Multiples of 3 and 5
If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23...

3 months ago

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Project Euler: Problem 10, Sum of Primes
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below the input, N. Thank you <http:/...

3 months ago

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Find vampire numbers
A vampire number is a number v that is the product of two numbers x and y such that the following conditions are satisfied: at ...

3 months ago

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Numbers with prime factors 2, 3 and 5.
Make a function which takes one positive integer n and returns a matrix with the numbers of the form (2^i)*(3^j)*(5^k) which are...

3 months ago

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Generalised Hamming Number
Inspired by Project Euler n°204 and Problem 1308 by James A generalised Hamming number of type n, has no prime factor larger ...

3 months ago

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Multiples of a Number in a Given Range
Given an integer factor _f_ and a range defined by _xlow_ and _xhigh_ inclusive, return a vector of the multiples of _f_ that fa...

3 months ago

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Proper Factors
Generate the proper factors of input integer x and return them in ascending order. For more information on proper factors, refer...

3 months ago

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Project Euler: Problem 3, Largest prime factor
The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number being input, input might be ui...

3 months ago

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Smith numbers
Return true if the input is a Smith number in base ten. Otherwise, return false. Read about Smith numbers at http://en.wikipedia...

3 months ago

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Get all prime factors
List the prime factors for the input number, in decreasing order. List each factor. If the prime factor occurs twice, list it as...

3 months ago

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Factorize THIS, buddy
List the prime factors for the input number, in decreasing order. List each factor only once, even if the factorization includes...

3 months ago

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Prime factor digits
Consider the following number system. Calculate the prime factorization for each number n, then represent the prime factors in a...

3 months ago