A126749 - OEIS

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

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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