A339040 Number of unlabeled connected simple graphs with n edges rooted at two noninterchangeable vertices.

1, 3, 10, 35, 125, 460, 1747, 6830, 27502, 113987, 485971, 2129956, 9591009, 44341610, 210345962, 1023182861, 5100235807, 26035673051, 136023990102, 726877123975, 3970461069738, 22156281667277, 126234185382902, 733899631974167, 4351500789211840

Offset

1,2

Links

Table of n, a(n) for n=1..25.

Formula

G.f.: f(x)/g(x) - r(x)^2 where f(x), g(x) and r(x) are the g.f.'s of A339063, A000664 and A339039.

Prog

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

Crossrefs

Cf. A000664, A002905, A303832, A304074, A339039, A339041, A339042, A339044, A339063.

Sequence in context: A224509 A026026 A047037 * A201058 A318113 A216710

Adjacent sequences: A339037 A339038 A339039 * A339041 A339042 A339043

Keyword

nonn

Author

Andrew Howroyd, Nov 20 2020

Status

approved