Solution to Hey, Look, a Grid!

by Iolanthe Chronis & Aaron Dinkin

All the prime factors of all the numbers in this grid are 2, 3, 5, 7, 11, 13, and the primes between 41 and 97. If, for any prime p in that set, you look at the set of cells in the grid that are divisible by p, you find that they form interesting shapes.

The primes between 41 and 97 form letters: So the set of cells divisible by 41 form the shape of an A, those divisible by 43 form a C, and on up to 97 which forms a Y. The full set of letters generated is ACEFIJLMOSTWY.

The primes between 2 and 13 form numbers: 89, 97, 43, 67, 47, and 53. The letters formed by 89, 97, 43, 67, 47, and 53 are, respectively, W, Y, C, L, E, and F. So the answer to the puzzle is WYCLEF.

2006 MIT Mystery Hunt