A126749 - OEIS

%I #7 Jul 22 2015 04:06:35

%S 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,

%T 2762,42,1,6,92,1631,23262,118114,50814,146,1,7,135,3643,101409,

%U 1686975,6530233,1420183,956

%N 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.

%C It is possible that the definition should say "connected" rather than "biconnected". Should be rechecked! - _Max Alekseyev_ and _Brendan McKay_, Jun 17 2008

%H Keith M. Briggs, <a href="http://keithbriggs.info/cgt.html">Combinatorial Graph Theory</a>

%e Triangle begins:

%e n=...1..2...3...4...5....6.....7......8........9........10

%e k.---------------------------------------------------------

%e 2|...0..0...0...1...1....5.....8.....42......146.......956

%e 3|...0..0...1...1...6...30...232...2762....50814...1420183

%e 4|...0..0...0...1...2...17...189...3627...118114...6530233

%e 5|...0..0...0...0...1....3....34....627....23262...1686975

%e 6|...0..0...0...0...0....1.....4.....59.....1631....101409

%e 7|...0..0...0...0...0....0.....1......5.......92......3643

%e 8|...0..0...0...0...0....0.....0......1........6.......135

%Y Diagonals give A126750-A126754.

%K nonn,tabl,more

%O 2,8

%A _N. J. A. Sloane_, Feb 18 2007