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 A361210 #64 Apr 09 2023 11:30:09
%S A361210 0,1,2,15,588,83295,40993230,70413420511,433343743592312,
%T A361210 9825711749274316671,840137012096473747415610,
%U A361210 275596225117501271622460109871,351011149451321734143551287903432452,1749719217881846572487198585072701742763487,34317835907818751756576624929762210160396817182918
%N A361210 Number of labeled digraphs on [n] with exactly 1 in-node and exactly 1 out-node.
%C A361210 Here, an in-node is a node whose outdegree is zero. An out-node is a node whose in-degree is zero. The in-node is not necessarily distinct from the out-node.
%H A361210 E. de Panafieu and S. Dovgal, <a href="https://arxiv.org/abs/1903.09454">Symbolic method and directed graph enumeration</a>, arXiv:1903.09454 [math.CO], 2019.
%H A361210 R. W. Robinson, <a href="http://cobweb.cs.uga.edu/~rwr/publications/components.pdf">Counting digraphs with restrictions on the strong components</a>, Combinatorics and Graph Theory '95 (T.-H. Ku, ed.), World Scientific, Singapore (1995), 343-354.
%t A361210 nn = 14; B[n_] := n! 2^Binomial[n, 2] ; e[z_] := Sum[z^n/B[n], {n, 0, nn}];
%t A361210 g[z_] := Sum[2^(n (n - 1)) z^n/B[n], {n, 0, nn}];egf[ggf_] := Normal[Series[ggf, {z, 0, nn}]] /. Table[z^i -> z^i*2^Binomial[i, 2], {i, 0, nn}];Table[n!, {n, 0, nn}] Map[Coefficient[#, u v] &, CoefficientList[Series[Exp[(u - 1) ( v - 1) z] egf[e[(u - 1) z] g[z] e[(v - 1) z]], {z, 0, nn}], z]]
%Y A361210 Cf. A086193 (no out-nodes nor in-nodes).
%K A361210 nonn
%O A361210 0,3
%A A361210 _Geoffrey Critzer_, Apr 09 2023