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 A339300 #6 Dec 22 2020 18:26:21
%S A339300 1,0,6,36,540,8400,169680,3966480,107518320,3295283040,112888369440,
%T A339300 4272403544640,177061349424960,7974538914101760,387840385867334400,
%U A339300 20257533315635616000,1130954856127948051200,67208532822729871372800,4235759061057115720128000
%N A339300 Number of essentially parallel oriented series-parallel networks with n labeled elements and without multiple unit elements in parallel.
%C A339300 See A339301 for additional details.
%F A339300 E.g.f. (1 + x)*exp(S(x)) - S(x) - 1 where S(x) is the e.g.f. of A339299.
%F A339300 E.g.f.: B(x)/(1 + B(x)) where B(x) is the e.g.f. of A339301.
%F A339300 E.g.f.: B(log(1+x)) where B(x) is the e.g.f. of A048174.
%o A339300 (PARI) seq(n, Z=x)={my(p=Z+O(x^2)); for(n=2, n, p = (1 + Z)*exp(p^2/(1+p)) - 1); Vec(serlaplace(1-1/(1+p)))}
%Y A339300 A048174 is the case with multiple edges in parallel allowed.
%Y A339300 A058379 is the case that order is not significant in series configurations.
%Y A339300 Cf. A339289 (unlabeled), A339299, A339301.
%K A339300 nonn
%O A339300 1,3
%A A339300 _Andrew Howroyd_, Dec 22 2020