Curious that so many of Russ's counts are squares: 1,-,4,-,-,-,100,225,-,1225,3136,7056 Rich -----Original Message----- From: Russ Cox To: njas@research.att.com Cc: math-fun; seqfan@ext.jussieu.fr Sent: 6/12/2004 10:46 AM Subject: Re: [math-fun] number of longest common substrings problem I think the C program below computes the initial terms of this sequence, for a two-character alphabet or an arbitrary alphabet. For a two-character alphabet: len 1: 1 lcs of length 1 for a a len 2: 2 lcs of length 1 for aa ab len 3: 4 lcs of length 2 for aab abb len 4: 10 lcs of length 2 for abba baab len 5: 24 lcs of length 2 for abbba baaab len 6: 46 lcs of length 3 for aabbba abaaab len 7: 100 lcs of length 4 for aaaaabb aabbbbb len 8: 225 lcs of length 4 for aaaaaabb aabbbbbb len 9: 525 lcs of length 5 for aaaaaaabb aaabbbbbb len 10: 1225 lcs of length 6 for aaaaaaabbb aaabbbbbbb len 11: 3136 lcs of length 6 for aaaaaaaabbb aaabbbbbbbb len 12: 7056 lcs of length 7 for aaaaaaaaabbb aaaabbbbbbbb <snip>