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A358243
Number of n-regular, N_0-weighted pseudographs on 2 vertices with total edge weight 3, up to isomorphism.
6
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
OFFSET
1,2
COMMENTS
Pseudographs are finite graphs with undirected edges without identity, where parallel edges between the same vertices and loops are allowed.
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
KEYWORD
nonn
AUTHOR
Lars Göttgens, Nov 04 2022
STATUS
approved