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A100548 Number of n-node labeled digraphs without endpoints. 3
1, 1, 1, 28, 2539, 847126, 987474781, 4267529230672, 71328353711113801, 4706871807383903992060, 1236666872833000506726110479, 1297665884376581511952494336126664, 5444003907104081585974782986977125743035, 91341304409373044577470623665964376840167100920 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

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

FORMULA

E.g.f.: exp(3/2*x^2)*(Sum_{n>=0} 2^(n*(n-1))*(x/exp(3*x))^n/n!)).

MATHEMATICA

m = 11;

egf = Exp[3x^2/2]*Sum[2^(n(n-1))*(x/Exp[3 x])^n/n!, {n, 0, m}];

a[n_] := SeriesCoefficient[egf, {x, 0, n}]*n!;

Table[a[n], {n, 0, m}] (* Jean-Fran├žois Alcover, Feb 23 2019 *)

PROG

(PARI) seq(n)={my(g=x/exp(3*x + O(x*x^n))); Vec(serlaplace(exp(3*x^2/2 + O(x*x^n))*sum(k=0, n, 2^(k*(k-1))*g^k/k!)))} \\ Andrew Howroyd, Jan 08 2020

CROSSREFS

Cf. A059167, A101388 (labeled case).

Sequence in context: A184134 A327294 A281137 * A103660 A317799 A275654

Adjacent sequences:  A100545 A100546 A100547 * A100549 A100550 A100551

KEYWORD

nonn

AUTHOR

Goran Kilibarda, Zoran Maksimovic, Vladeta Jovovic, Jan 02 2005

EXTENSIONS

Terms a(12) and beyond from Andrew Howroyd, Jan 08 2020

STATUS

approved

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Last modified July 26 20:29 EDT 2021. Contains 346295 sequences. (Running on oeis4.)