A126749 Triangle read by rows: T(n,k) (n>=2, k=0..n-1) gives number of biconnected graphs on n nodes with chromatic number n-k.

0, 1, 0, 1, 1, 1, 1, 2, 6, 1, 1, 3, 17, 30, 5, 1, 4, 34, 189, 232, 8, 1, 5, 59, 627, 3627, 2762, 42, 1, 6, 92, 1631, 23262, 118114, 50814, 146, 1, 7, 135, 3643, 101409, 1686975, 6530233, 1420183, 956

Offset

2,8

Comments

It is possible that the definition should say "connected" rather than "biconnected". Should be rechecked! - Max Alekseyev and Brendan McKay, Jun 17 2008

Links

Table of n, a(n) for n=2..46.

Keith M. Briggs, Combinatorial Graph Theory

Example

Triangle begins:
n=...1..2...3...4...5....6.....7......8........9........10
k.---------------------------------------------------------
2|...0..0...0...1...1....5.....8.....42......146.......956
3|...0..0...1...1...6...30...232...2762....50814...1420183
4|...0..0...0...1...2...17...189...3627...118114...6530233
5|...0..0...0...0...1....3....34....627....23262...1686975
6|...0..0...0...0...0....1.....4.....59.....1631....101409
7|...0..0...0...0...0....0.....1......5.......92......3643
8|...0..0...0...0...0....0.....0......1........6.......135

Crossrefs

Diagonals give A126750-A126754.

Sequence in context: A065529 A205015 A204937 * A024573 A191359 A339766

Adjacent sequences: A126746 A126747 A126748 * A126750 A126751 A126752

Keyword

nonn,tabl,more

Author

N. J. A. Sloane, Feb 18 2007

Status

approved