A281003 a(n) is the number of unlabeled simple graphs with n vertices that have no automorphisms of odd parity.

1, 0, 0, 1, 6, 28, 252, 4726, 150324, 8308928, 817860888, 144938364368, 46784208920560, 27789645300385184, 30630702203393521120, 63070163901389334212336, 243902725979609232729020320, 1779250465648201682685291759744

Offset

1,5

Links

Table of n, a(n) for n=1..18.

Brendan McKay, Isoclasses of simple graphs

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

Adjacent sequences: A281000 A281001 A281002 * A281004 A281005 A281006

Keyword

nonn

Author

Mariano Suárez-Álvarez, Jan 12 2017

Extensions

More terms from Ira M. Gessel, May 30 2019

Status

approved