The OEIS is supported by the many generous donors to the OEIS Foundation.
%I #14 Dec 02 2022 13:29:04
%S 1,4,9,15,21,28,34,41,47,54,60,67,73,80,86,93,99,106,112,119,125,132,
%T 138,145,151,158,164,171,177,184,190,197,203,210,216,223,229,236,242,
%U 249,255,262,268,275,281,288,294,301,307,314,320,327,333,340,346,353
%N Number of n-regular, N_0-weighted pseudographs on 2 vertices with total edge weight 3, up to isomorphism.
%C Pseudographs are finite graphs with undirected edges without identity, where parallel edges between the same vertices and loops are allowed.
%F Apparently a(n) = A258589(n-2) + 2 for n>= 4, i.e., terms satisfy linear recurrence a(n) = a(n-1) + a(n-2) - a(n-3) for n>=7. - _Hugo Pfoertner_, Dec 02 2022
%Y Other total edge weights 4 (A358244), 5 (A358245), 6 (A358246), 7 (A358247), 8 (A358248), 9 (A358249).
%Y Cf. A258589.
%K nonn
%O 1,2
%A _Lars Göttgens_, Nov 04 2022