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 A303829 #12 May 04 2018 04:48:21 %S A303829 0,2,6,28,148,1144,13128,250240,8295664,494367376,53628829952, %T A303829 10655018252544,3893626388008448,2627758027841688960, %U A303829 3289042848785452985600,7666804477507744021487616,33416397343695235205887366144,273365202164844511328577434284160 %N A303829 Birooted graphs: number of unlabeled graphs with n nodes rooted at 2 indistinguishable roots. %F A303829 a(n) = 2 * A126122(n). - _Alois P. Heinz_, May 01 2018 %Y A303829 Cf. A303831 (connected), A303833 (trees), A126122. %K A303829 nonn %O A303829 1,2 %A A303829 _Brendan McKay_, May 01 2018