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 A339299 #6 Dec 22 2020 18:26:14
%S A339299 0,2,6,72,840,14040,276360,6494880,175452480,5375311200,183962227680,
%T A339299 6958070380800,288200792880000,12974113884251520,630742839699772800,
%U A339299 32933429270386444800,1838083950894102912000,109201772719684867622400,6880730833827011402841600
%N A339299 Number of essentially series oriented series-parallel networks with n labeled elements and without multiple unit elements in parallel.
%C A339299 See A339301 for additional details.
%F A339299 E.g.f.: P(x)^2/(1 - P(x)) where P(x) is the e.g.f. of A339300.
%F A339299 E.g.f.: B(x)^2/(1 + B(x)) where B(x) is the e.g.f. of A339301.
%F A339299 E.g.f.: B(log(1+x)) where x + B(x) is the e.g.f. of A058349.
%o A339299 (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(p-p/(1+p)), -n)}
%Y A339299 A058349 is the case with multiple unit elements in parallel allowed.
%Y A339299 A058380 is the case that order is not significant in series configurations.
%Y A339299 Cf. A339288 (unlabeled), A339300, A339301.
%K A339299 nonn
%O A339299 1,2
%A A339299 _Andrew Howroyd_, Dec 22 2020