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A053598 Number of n-node unlabeled digraphs without isolated nodes. 3
1, 0, 2, 13, 202, 9390, 1531336, 880492496, 1792477159408, 13026163465206704, 341247403996148180800, 32522568124623933138617088, 11366712907916015518547782806784, 14669074325967499043636521641422216704, 70315641946149306808455637518883828774996992 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Equals first differences of A000273.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..35

FORMULA

O.g.f.: A(x)*(1-x) where A(x) is o.g.f. for A000273. - Geoffrey Critzer, Oct 09 2012

MATHEMATICA

Needs["Combinatorica`"];

nn=15; s=Sum[NumberOfDirectedGraphs[n]x^n, {n, 0, nn}]; CoefficientList[Series[s (1-x), {x, 0, nn}], x]  (* Geoffrey Critzer, Oct 09 2012 *)

Join[{1}, Table[GraphPolynomial[n, x, Directed] /. x -> 1, {n, 0, 15}] // Differences] (* Jean-Fran├žois Alcover, Feb 04 2015 *)

CROSSREFS

Cf. A002494.

Sequence in context: A049512 A003507 A003085 * A193550 A102585 A227746

Adjacent sequences:  A053595 A053596 A053597 * A053599 A053600 A053601

KEYWORD

nonn,nice

AUTHOR

Vladeta Jovovic, Apr 10 2000

STATUS

approved

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Last modified November 14 06:14 EST 2018. Contains 317162 sequences. (Running on oeis4.)