A084269 - OEIS

A084269

Triangle read by rows: T(n,k) is the number of simple connected graphs on n unlabeled nodes having chromatic number k, 1 <= k <= n.

1, 0, 1, 0, 1, 1, 0, 3, 2, 1, 0, 5, 12, 3, 1, 0, 17, 64, 26, 4, 1, 0, 44, 475, 282, 46, 5, 1, 0, 182, 5036, 5009, 809, 74, 6, 1, 0, 730, 80947, 149551, 27794, 1940, 110, 7, 1, 0, 4032, 2010328, 7694428, 1890221, 113272, 4125, 156, 8, 1, 0, 25598, 76115143, 667036310, 248580644, 14545025, 389583, 8040, 212, 9, 1

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OFFSET

1,8

LINKS

Sean A. Irvine, Table of n, a(n) for n = 1..78

Eric Weisstein's World of Mathematics, n-Chromatic Graph

EXAMPLE

Triangle begins:

0, 1;

0, 1, 1;

0, 3, 2, 1;

0, 5, 12, 3, 1;