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 A287007 #13 Feb 16 2025 08:33:46 %S A287007 1,2,4,11,33,152,1006,11808,257625,11018264 %N A287007 Number of simple (not necessarily connected) graphs on n vertices whose fractional chromatic number equals its (integer) chromatic number. %C A287007 First differs from A198634 (weakly perfect graphs) at a(8). The three 8-node graphs that have equal chromatic and fractional chromatic numbers but are not weakly perfect are the 4-antiprism graph and 50- and 84-Johnson solid skeleton graphs, all of which have clique number 3 but chromatic and fractional chromatic number 4. %H A287007 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ChromaticNumber.html">Chromatic Number</a> %H A287007 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FractionalChromaticNumber.html">Fractional Chromatic Number</a> %F A287007 a(n) = A243252(n) + A287008(n). %Y A287007 Cf. A198634 (number of weakly perfect graphs on n nodes). %Y A287007 Cf. A243252 (number of simple connected graphs on n nodes with fractional chromatic number equal to chromatic number). %Y A287007 Cf. A287008 (number of simple disconnected graphs on n nodes with fractional chromatic number equal to chromatic number). %K A287007 nonn,more %O A287007 1,2 %A A287007 _Eric W. Weisstein_, May 17 2017