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 A123543 Number of connected labeled 2-regular pseudodigraphs (multiple arcs and loops allowed) of order n. 4
 0, 1, 2, 14, 201, 4704, 160890, 7538040, 462869190, 36055948320, 3474195588360, 405786523413600, 56502317464777800, 9248640671612865600, 1758505909558569771600, 384399253128691423022400 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1982. LINKS R. W. Robinson, Table of n, a(n) for n = 0..48 FORMULA E.g.f.: log(1 + Sum_{k>0} A000681(k)*x^k/k!). - Andrew Howroyd, Sep 09 2018 MATHEMATICA m = 16; a681[n_] := n!*HypergeometricPFQ[{1/2, -n}, {}, -2]/2^n; egf = Log[1 + Sum[a681[k] x^k/k!, {k, 1, m}]]; CoefficientList[egf + O[x]^m, x] Range[0, m-1]! (* Jean-François Alcover, Aug 26 2019 *) PROG (PARI) seq(n)={Vec(serlaplace(log(serlaplace(exp(x/2 + O(x*x^n))/sqrt(1-x + O(x*x^n))))), -(n+1))}; \\ Andrew Howroyd, Sep 09 2018 CROSSREFS Connected version of A000681. First column of A307804. Cf. A123544. Sequence in context: A213977 A322196 A102224 * A279452 A262008 A054652 Adjacent sequences: A123540 A123541 A123542 * A123544 A123545 A123546 KEYWORD nonn AUTHOR N. J. A. Sloane, Nov 13 2006 STATUS approved

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Last modified December 1 21:09 EST 2022. Contains 358484 sequences. (Running on oeis4.)