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 A102580 #8 Jan 20 2024 13:52:43
%S A102580 1,1,3,27,2025,566190,625831920,2774192113350,49208948146347570,
%T A102580 3472093007861482740960,971461407155771477392032600,
%U A102580 1076446082528185671934674675023160,4723701978908086606944984284949329285400,82155133922723780601138029235949809990647219040
%N A102580 Number of n-node labeled connected digraphs whose underlying graphs are mating graphs, cf. A006024.
%H A102580 Andrew Howroyd, <a href="/A102580/b102580.txt">Table of n, a(n) for n = 0..50</a>
%F A102580 E.g.f.: 1 + x + log(B(x)/(1 + x)) where B(x) is the e.g.f. of A102579. - _Andrew Howroyd_, Jan 20 2024
%o A102580 (PARI) \\ b(n) is A102579(n); permcount, edges defined in A369283.
%o A102580 b(n) = {my(s=0); forpart(p=n, s += permcount(p)*(-1)^(n-#p)*edges(p, w->1 + 3^w)); s}
%o A102580 seq(n) = {Vec(serlaplace(1 + x + log(sum(k=0, n, b(k)*x^k/k!, O(x*x^n))/(1 + x))))} \\ _Andrew Howroyd_, Jan 20 2024
%Y A102580 Cf. A006024, A102579 (not necessarily connected), A102597 (oriented), A102598 (unlabeled), A369283.
%K A102580 nonn
%O A102580 0,3
%A A102580 Goran Kilibarda, Zoran Maksimovic, _Vladeta Jovovic_, Jan 21 2005
%E A102580 a(0)=1 prepended and a(12) onwards from _Andrew Howroyd_, Jan 20 2024