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

Offset

0,8

Links

Table of n, a(n) for n=0..65.

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

Example

Triangle begins:
  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;
  ...

Crossrefs

Row sums are A001349.

Columns k=3..7 are A126737, A126738, A126739, A126740, A241702.

Partial row sums include A005142, A076322, A076323, A076324, A076325, A076326, A076327, A076328.

Essentially the same table as A126736.

Cf. A084268 (not necessarily connected), A115597.

Sequence in context: A344348 A179753 A279318 * A051427 A194763 A194741

Adjacent sequences: A084266 A084267 A084268 * A084270 A084271 A084272

Keyword

nonn,tabl

Author

Eric W. Weisstein, May 24 2003

Extensions

a(37)-a(66) from Andrew Howroyd, Dec 02 2018

Status

approved