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A339040
Number of unlabeled connected simple graphs with n edges rooted at two noninterchangeable vertices.
6
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
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)}
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Nov 20 2020
STATUS
approved