This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A084269 #13 Feb 16 2025 08:32:49 %S A084269 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, %T A084269 182,5036,5009,809,74,6,1,0,730,80947,149551,27794,1940,110,7,1,0, %U A084269 4032,2010328,7694428,1890221,113272,4125,156,8,1,0,25598,76115143,667036310,248580644,14545025,389583,8040,212,9,1 %N 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. %H A084269 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/n-ChromaticGraph.html">n-Chromatic Graph</a> %e A084269 Triangle begins: %e A084269 1; %e A084269 0, 1; %e A084269 0, 1, 1; %e A084269 0, 3, 2, 1; %e A084269 0, 5, 12, 3, 1; %e A084269 0, 17, 64, 26, 4, 1; %e A084269 0, 44, 475, 282, 46, 5, 1; %e A084269 0, 182, 5036, 5009, 809, 74, 6, 1; %e A084269 0, 730, 80947, 149551, 27794, 1940, 110, 7, 1; %e A084269 ... %Y A084269 Row sums are A001349. %Y A084269 Columns k=3..7 are A126737, A126738, A126739, A126740, A241702. %Y A084269 Partial row sums include A005142, A076322, A076323, A076324, A076325, A076326, A076327, A076328. %Y A084269 Essentially the same table as A126736. %Y A084269 Cf. A084268 (not necessarily connected), A115597. %K A084269 nonn,tabl %O A084269 0,8 %A A084269 _Eric W. Weisstein_, May 24 2003 %E A084269 a(37)-a(66) from _Andrew Howroyd_, Dec 02 2018