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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.

%I A126749 #7 Jul 22 2015 04:06:35
%S A126749 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 A126749 2762,42,1,6,92,1631,23262,118114,50814,146,1,7,135,3643,101409,
%U A126749 1686975,6530233,1420183,956
%N 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.
%C A126749 It is possible that the definition should say "connected" rather than "biconnected". Should be rechecked! - _Max Alekseyev_ and _Brendan McKay_, Jun 17 2008
%H A126749 Keith M. Briggs, <a href="http://keithbriggs.info/cgt.html">Combinatorial Graph Theory</a>
%e A126749 Triangle begins:
%e A126749 n=...1..2...3...4...5....6.....7......8........9........10
%e A126749 k.---------------------------------------------------------
%e A126749 2|...0..0...0...1...1....5.....8.....42......146.......956
%e A126749 3|...0..0...1...1...6...30...232...2762....50814...1420183
%e A126749 4|...0..0...0...1...2...17...189...3627...118114...6530233
%e A126749 5|...0..0...0...0...1....3....34....627....23262...1686975
%e A126749 6|...0..0...0...0...0....1.....4.....59.....1631....101409
%e A126749 7|...0..0...0...0...0....0.....1......5.......92......3643
%e A126749 8|...0..0...0...0...0....0.....0......1........6.......135
%Y A126749 Diagonals give A126750-A126754.
%K A126749 nonn,tabl,more
%O A126749 2,8
%A A126749 _N. J. A. Sloane_, Feb 18 2007