A339064 Number of unlabeled simple graphs with n edges rooted at two indistinguishable vertices.

1, 3, 9, 28, 87, 276, 909, 3086, 10879, 39821, 151363, 597062, 2442044, 10342904, 45301072, 204895366, 955661003, 4590214994, 22675644514, 115068710553, 599149303234, 3197694533771, 17475917252052, 97712883807625, 558481251055893, 3260409769087068

Offset

0,2

Links

Table of n, a(n) for n=0..25.

Example

The a(1) = 3 cases correspond to a single edge which can be attached to zero, one or both of the roots.

Prog

(PARI) \\ See A339063 for G.
seq(n)={my(A=O(x*x^n)); Vec((G(2*n, x+A, [1, 1]) + G(2*n, x+A, [2]))/2)}

Crossrefs

Cf. A000664, A053419 (one root), A303829, A339041, A339063, A339065.

Sequence in context: A085839 A115239 A134915 * A118365 A095716 A124820

Adjacent sequences: A339061 A339062 A339063 * A339065 A339066 A339067

Keyword

nonn

Author

Andrew Howroyd, Nov 22 2020

Status

approved