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 A289678 #18 Aug 04 2017 04:14:13 %S A289678 1,1,3,6,15,42,131,442,1551,5723,22171,89156,370199,1589240,7020127, %T A289678 31906974 %N A289678 Number of hypermaps which are self-equivalent with respect to reversing the colors of the nodes and which have n edges. %H A289678 M. Deryagina, <a href="ftp://ftp.pdmi.ras.ru/pub/publicat/znsl/v446/p031.pdf">On the enumeration of hypermaps which are self-equivalent with respect to reversing the colors of vertices</a>, Preprint 2016. %F A289678 a(n) = 2*A234278(n) - 2*A057005(n). %Y A289678 Cf. A057005, A234278. %K A289678 nonn,more %O A289678 1,3 %A A289678 _N. J. A. Sloane_, Aug 03 2017