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 A258719 #8 May 06 2023 17:24:11 %S A258719 0,0,9,16192,198862625,42002510818752,207278622607612079818, %T A258719 29215384735442091573649485568, %U A258719 137562588659577384442574662095693261747,24724406349174154904254665510689036571978910174560 %N A258719 Number of self-dual noncommutative groupoids with n elements. %H A258719 N. J. A. Sloane, <a href="/A001329/a001329.jpg">Overview of A001329, A001423-A001428, A258719, A258720.</a> %H A258719 T. Tamura, <a href="/A001329/a001329.pdf">Some contributions of computation to semigroups and groupoids</a>, pp. 229-261 of J. Leech, editor, Computational Problems in Abstract Algebra. Pergamon, Oxford, 1970. (Annotated and scanned copy) %F A258719 a(n) = A029850(n) - A001425(n). - _Andrew Howroyd_, May 06 2023 %Y A258719 Cf. A029850, A001425, A258720. %K A258719 nonn,more %O A258719 1,3 %A A258719 _N. J. A. Sloane_, Jun 18 2015 %E A258719 a(5)-a(10) from _Andrew Howroyd_, May 06 2023