Problem 2910. Mersenne Primes vs. All Primes
A Mersenne prime (M) is a prime number of the form M = 2^p - 1, where p is another prime number. Problem 525 asks the user to determine if a number is a Mersenne prime. In this problem, you are tasked with returning the number of primes numbers below the input number, n, that are Mersenne primes and the fraction of all primes below that input number that the Mersenne primes represent.
For example, for n = 100, there are 25 primes numbers: 2, 3, 5, 7, ..., 89, 97. As far as Mersenne primes go, there are only three that are less than 100: 2^2 - 1 = 3, 2^3 - 1 = 7, and 2^5 - 1 = 31. The corresponding fraction would be 3/25.
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Hello Grant,
I don't know if it's a lot of work but it could be a good idea to add a Prime Numbers group 2 with more difficult problems. I think about beautiful Ned's problems (primes ladders, Longest prime diagonal, Twins in a window ...).
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Indexing II
- 22 Problems
- 161 Finishers
- Getting the indices from a vector
- Symmetry of vector
- Calculate the Number of Sign Changes in a Row Vector (No Element Is Zero)
- Count consecutive 0's in between values of 1
- Find last zero for each column
- Oh Zero Zero Zero!!!
- Create an index-powered vector
- Find nth maximum
- Decimation - Optimized for speed
- Unique values without using UNIQUE function
- Symmetry of vector
- Generate a vector like 1,2,2,3,3,3,4,4,4,4
- Create an n-by-n null matrix and fill with ones certain positions
- Implement a bubble sort technique and output the number of swaps required
- Create a vector whose elements depend on the previous element
- Set a diagonal
- Unique values without using UNIQUE function
- Generate a vector like 1,2,2,3,3,3,4,4,4,4
- Change the sign of even index entries of the reversed vector
- Decimation
- Insert zeros into vector
- Reference Index Number
- Determine the number of odd integers in a vector
- Max index of 3D array
- Finding peaks
- Getting the indices from a vector
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