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A281003
a(n) is the number of unlabeled simple graphs with n vertices that have no automorphisms of odd parity.
0
1, 0, 0, 1, 6, 28, 252, 4726, 150324, 8308928, 817860888, 144938364368, 46784208920560, 27789645300385184, 30630702203393521120, 63070163901389334212336, 243902725979609232729020320, 1779250465648201682685291759744
OFFSET
1,5
MATHEMATICA
(* This assumes you have Brendan McKay's files listing isoclasses of simple graphs (see link), and starts from a(2), as there is no graph1.g6 *)
Table[
Length@ Select[
Import["graph" <> ToString[i] <> ".g6"],
Function[g,
! AnyTrue[GroupElements[GraphAutomorphismGroup[g]],
Apply[Times, (-1)^(Length /@ First[#] - 1)] == -1 &]
]
],
{i, 2, 9}
]
CROSSREFS
Sequence in context: A216413 A090898 A134872 * A049603 A333927 A035527
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Ira M. Gessel, May 30 2019
STATUS
approved