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 A339038 #16 Feb 26 2023 14:39:29
%S A339038 1,2,7,23,88,339,1396,5915,26080,118539,555678,2678458,13262193,
%T A339038 67353325,350493424,1866989802,10171394388,56631507822,322011612423,
%U A339038 1868702977253,11061267210030,66745602611831,410360493588788,2569318971123439,16374787277199728,106180292431149021
%N A339038 Number of unlabeled connected loopless multigraphs with n edges rooted at one unoriented edge.
%F A339038 G.f.: x*f(x)/g(x) where f(x) is the g.f. of A339066 and g(x) is the g.f. of A050535.
%t A339038 seq[n_] := (G[2n, x + O[x]^n, {1, 1}] + G[2n, x + O[x]^n, {2}])/G[2n, x + O[x]^n, {}] // CoefficientList[#/2, x]&;
%t A339038 seq[15] (* _Jean-François Alcover_, Dec 02 2020, after _Andrew Howroyd_'s code for G in A339065 *)
%o A339038 (PARI) \\ See A339065 for G.
%o A339038 seq(n)={my(A=O(x*x^n)); Vec((G(2*n, x+A, [1,1]) + G(2*n, x+A, [2]))/G(2*n, x+A, []))/2}
%Y A339038 Cf. A050535, A076864, A303832, A339036, A339037, A339042, A339043, A339065, A339066.
%K A339038 nonn
%O A339038 1,2
%A A339038 _Andrew Howroyd_, Nov 20 2020