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 A361412 #7 Mar 13 2023 13:29:22 %S A361412 1,3,12,67,441,3464,31616,331997,3961462,53105424,791237787, %T A361412 12978022526,232407307054,4511887729886,94385418177277, %U A361412 2116529900006321,50646269987874834,1288091152941695791,34697173459041347465,986800102740080746702,29548269236430810895013 %N A361412 Number of connected 3-regular multigraphs on 2n unlabeled nodes rooted at an unoriented edge (or loop), loops allowed. %C A361412 a(0) = 1 by convention. Loops add two to the degree of a node. %C A361412 a(n) is also the number of connected multigraphs on 2*n+1 unlabeled nodes with one vertex of degree 2 and all others of degree 3, loops allowed. %e A361412 The a(1) = 3 multigraphs correspond to either a triple edge rooted on one of the edges or to a single edge with a loop at each end and rooted on either the edge or the loop. %Y A361412 A361135 is the 4-regular version. %Y A361412 Cf. A005967 (unrooted), A129427, A361446, A361447, A361448. %K A361412 nonn %O A361412 0,2 %A A361412 _Andrew Howroyd_, Mar 12 2023