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 A339286 #7 Nov 30 2020 21:40:39
%S A339286 0,1,4,17,62,255,1026,4363,18656,81446,357708,1584110,7042396,
%T A339286 31429998,140626375,630640342,2833200433,12748771157,57445747751,
%U A339286 259170739397,1170566884224,5292311737901,23949417255984,108470668735077,491664303153769,2230174016940385,10122784007130716
%N A339286 Total number of interior vertices in the multigraphs of all unoriented series-parallel networks with n edges.
%C A339286 See A339285 for additional details.
%F A339286 a(n) = Sum_{k=1..n-1} k*A339285(n,k).
%o A339286 (PARI) \\ See A339285 for VertexWeighted.
%o A339286 seq(n)={subst(deriv(VertexWeighted(n,x,y)), y, 1)}
%Y A339286 Cf. A339225, A339232, A339285.
%K A339286 nonn
%O A339286 1,3
%A A339286 _Andrew Howroyd_, Nov 30 2020