A180260 - OEIS

A180260

Number of not necessarily connected 8-regular simple graphs on n vertices.

1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 6, 94, 10786, 3459386, 1470293676, 733351105935, 423187422492342, 281341168330848874, 214755319657939505396, 187549729101764460261505, 186685399408147545744203915, 210977245260028917322933165888

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OFFSET

0,12

COMMENTS

The Euler transformation currently does nothing: for n < 18, a(n) = A014378(n).

LINKS

Table of n, a(n) for n=0..22.

Eric Weisstein's World of Mathematics, Octic Graph

FORMULA

Euler transformation of A014378.

EXAMPLE

The a(0)=1 graph is K_0 (vacuously 8-regular).

The a(9)=1 graph is K_9.

MATHEMATICA

A014378 = Cases[Import["https://oeis.org/A014378/b014378.txt", "Table"], {_, _}][[All, 2]];

(* EulerTransform is defined in A005195 *)

EulerTransform[Rest @ A014378] (* Jean-François Alcover, Dec 04 2019, updated Mar 18 2020 *)

CROSSREFS

8-regular simple graphs: A014378 (connected), A165878 (disconnected), this sequence (not necessarily connected).

Not necessarily connected regular simple graphs: A005176 (any degree), A051031 (triangular array), specified degree k: A000012 (k=0), A000012 (k=1), A008483 (k=2), A005638 (k=3), A033301 (k=4), A165626 (k=5), A165627 (k=6), A165628 (k=7), this sequence (k=8).

8-regular not necessarily connected graphs: this sequence (simple graphs), A129437 (multigraphs with loops allowed), A129426 (multigraphs with loops forbidden).

Sequence in context: A184980 A184981 A014378 * A058465 A290984 A338788

Adjacent sequences: A180257 A180258 A180259 * A180261 A180262 A180263

KEYWORD

nonn,hard

AUTHOR

Jason Kimberley, Jan 17 2011

EXTENSIONS

a(17)-a(22) from Andrew Howroyd, Mar 08 2020

STATUS

approved