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A052170

Number of directed loopless multigraphs with n arcs.

1, 1, 6, 24, 130, 688, 4211, 26840, 184153, 1328155, 10078617, 79926478, 660616432, 5671793248, 50459837996, 464139053799, 4405521306315, 43077862741114, 433275511964227, 4476516495577776, 47451864583578111, 515494036824348917, 5733423512317010811, 65226494052113260251, 758377712833720838677, 9004484581478188581057

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,3

LINKS

Andrew Howroyd, Table of n, a(n) for n = 0..50

FORMULA

a(n) = A333361(n, 2*n). - Andrew Howroyd, Mar 16 2020

PROG

(PARI) a(n)={polcoef(G(2*n, x + O(x*x^(n))), n)} \\ Needs G from A333361. - Andrew Howroyd, Mar 16 2020

(PARI) \\ faster, also needs G from A333361.

EulerT(v)={Vec(exp(x*Ser(dirmul(v, vector(#v, n, 1/n))))-1, -#v)}

InvEulerMT(u)={my(n=#u, p=log(1+x*Ser(u)), vars=variables(p)); Vec(sum(i=1, n, moebius(i)*substvec(p + O(x*x^(n\i)), vars, apply(v->v^i, vars))/i))}