A358243 - OEIS

A358243

Number of n-regular, N_0-weighted pseudographs on 2 vertices with total edge weight 3, up to isomorphism.

1, 4, 9, 15, 21, 28, 34, 41, 47, 54, 60, 67, 73, 80, 86, 93, 99, 106, 112, 119, 125, 132, 138, 145, 151, 158, 164, 171, 177, 184, 190, 197, 203, 210, 216, 223, 229, 236, 242, 249, 255, 262, 268, 275, 281, 288, 294, 301, 307, 314, 320, 327, 333, 340, 346, 353

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Pseudographs are finite graphs with undirected edges without identity, where parallel edges between the same vertices and loops are allowed.

LINKS

Table of n, a(n) for n=1..56.

FORMULA

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

CROSSREFS

Other total edge weights 4 (A358244), 5 (A358245), 6 (A358246), 7 (A358247), 8 (A358248), 9 (A358249).

Cf. A258589.

Sequence in context: A313297 A270545 A359626 * A099055 A162801 A335250

Adjacent sequences: A358240 A358241 A358242 * A358244 A358245 A358246

KEYWORD

nonn

AUTHOR

Lars Göttgens, Nov 04 2022

STATUS

approved