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A339037
Number of unlabeled connected loopless multigraphs with n edges rooted at one oriented edge.
6
1, 3, 11, 41, 160, 641, 2672, 11479, 50938, 232830, 1095151, 5292990, 26257328, 133548307, 695752146, 3709509938, 20224607541, 112675185837, 641016837378, 3721624588590, 22037618432547, 133023405207408, 818085097509494, 5123460267381837, 32660335570381961, 211825198708110059
OFFSET
1,2
FORMULA
G.f.: x*f(x)/g(x) where f(x) is the g.f. of A339065 and g(x) is the g.f. of A050535.
MATHEMATICA
seq[n_] := Module[{A = O[x]^n}, G[2n, x+A, {1, 1}]/G[2n, x+A, {}] // CoefficientList[#, x]&]; (* Jean-François Alcover, Dec 02 2020, after Andrew Howroyd's code for G in A339065 *)
PROG
(PARI) \\ See A339065 for G.
seq(n)={my(A=O(x*x^n)); Vec(G(2*n, x+A, [1, 1])/G(2*n, x+A, []))}
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Nov 20 2020
STATUS
approved