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 A378431 #10 May 27 2025 14:57:50
%S A378431 1,727,580369,943372583,4393791394153,73031427044945215,
%T A378431 4761040298703872985897,1242974526675429334954640663,
%U A378431 1300665117895338817158343055376913,5449895182361696580039591706226169477735,91388720915969010273161845143264574586208701497
%N A378431 Number of cyclic edge cuts in the n-barbell graph.
%H A378431 Andrew Howroyd, <a href="/A378431/b378431.txt">Table of n, a(n) for n = 3..50</a>
%H A378431 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/BarbellGraph.html">Barbell Graph</a>.
%H A378431 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CyclicEdgeCut.html">Cyclic Edge Cut</a>.
%F A378431 a(n) = 4*A001858(n)*A378324(n) + 2*(A006125(n)-A001858(n))^2 - (Sum_{k=1..n} binomial(n-1,k-1)*(A001187(k)-A000272(k))*A001858(n-k))^2. - _Andrew Howroyd_, May 27 2025
%o A378431 (PARI)
%o A378431 scs(p,q=p) = {serconvol(serlaplace(p),serlaplace(q))}
%o A378431 seq(n)={my(g=sum(k=0,n,2^binomial(k,2)*x^k/k!, O(x*x^n)), t=sum(k=1,n,k^(k-2)*x^k/k!, O(x*x^n))); Vec( 4*scs(exp(t), g - (1+log(g)-t)*exp(t)) + 2*scs(g-exp(t)) - scs(intformal(exp(t)*deriv(log(g)-t))) )} \\ _Andrew Howroyd_, May 27 2025
%Y A378431 Cf. A000272, A001187, A006125, A001858, A378324.
%K A378431 nonn
%O A378431 3,2
%A A378431 _Eric W. Weisstein_, Nov 26 2024
%E A378431 a(6) onwards from _Andrew Howroyd_, May 27 2025