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A339064 Number of unlabeled simple graphs with n edges rooted at two indistinguishable vertices. 4
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified July 28 07:09 EDT 2021. Contains 346317 sequences. (Running on oeis4.)