The ascending sequence of positive integers divisible only by 2, 3, and 5. Writing a computer program to generate the sequence (in sorted order!) is nontrivial. While the problem used to be a poster child for the co-routines crowd, today it is often mentioned as an application of lazy evaluation.

The first 20 elements of the Hamming sequence are `1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24, 25, 27, 30, 32, 36`. This was computed by a (clearly-written!) 47-line functional Perl program.