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 A380197 #35 Jan 23 2025 00:03:40
%S A380197 1,1,3,25,423,16261,1266843,200830225,65750156223,42834021462061,
%T A380197 55174125327583923
%N A380197 Number of ways to choose a simple labeled graph on [n] and properly color the vertices using the minimum number of colors.
%C A380197 a(n) is the chromatic polynomial evaluated at the chromatic number of a graph summed over all simple labeled graphs on [n].
%H A380197 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ChromaticNumber.html">Chromatic Number</a>.
%H A380197 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ChromaticPolynomial.html">Chromatic Polynomial</a>.
%t A380197 (* this code only returns a(0) - a(7) using precomputed data in Mathematica 12 *)
%t A380197 nog = {1, 2, 4, 11, 34, 156, 1044}; Prepend[Table[Total[n!/Table[GraphData[{n, i},AutomorphismCount"], {i, 1, nog[[n]]}]*Table[GraphData[{n, i},ChromaticPolynomial"][GraphData[{n, i}, "ChromaticNumber"]], {i, 1, nog[[n]]}]], {n, 1, 7}],1]
%Y A380197 Cf. A006125, A372920, A229048, A084268.
%K A380197 nonn,more
%O A380197 0,3
%A A380197 _Geoffrey Critzer_, Jan 22 2025
%E A380197 a(8)-a(10) from _Andrew Howroyd_, Jan 22 2025