Problem 18 Maximum path sum I
Problem 18: Maximum path sum I
By starting at the top of the triangle below and moving to adjacent numbers on th[……]
Problem 17 Number letter counts
Problem 17: Number letter counts
If the numbers 1 to 5 are written out in words: one, two, three, four, five, th[……]
Problem 16 Power digit sum
Problem 16: Power digit sum
215 = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26.
What is the sum of[……]
Problem 15 Lattice paths
Problem 15: Lattice paths
Starting in the top left corner of a 2×2 grid, and only being able to move to the righ[……]
Problem 14 Longest Collatz sequence
Problem 14: Longest Collatz sequence
The following iterative sequence is defined for the set of positive integer[……]
Problem 13 Large sum
Problem 13: Large sum
Work out the first ten digits of the sum of the following one-hundred 50-digit numbers.
37[……]
Problem 12 Highly divisible triangular number
Problem 12: Highly divisible triangular number
The sequence of triangle numbers is generated by adding the natur[……]
Problem 11 Largest product in a grid
Problem 11: Largest product in a grid
In the 20×20 grid below, four numbers along a diagonal line have been mark[……]
Problem 10 Summation of primes
Problem 10: Summation of primes
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
Find the sum of all the pr[……]
Problem 9 Special Pythagorean triplet
Problem 9: Special Pythagorean triplet
A Pythagorean triplet is a set of three natural numbers, a < b < c,[……]
Problem 8 Largest product in a series
Problem 8: Largest product in a series
The four adjacent digits in the 1000-digit number that have the greatest p[……]
Problem 7 10001st prime
Problem 7: 10001st prime
By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th[……]
Problem 6 Sum square difference
Problem 6: Sum square difference
The sum of the squares of the first ten natural numbers is,
12 + 22 + … + 102[……]
Problem 5 Smallest multiple
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 sm[……]
Problem 4 Largest palindrome product
Problem 4: Largest palindrome product
A palindromic number reads the same both ways. The largest palindrome made[……]