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 A053549 Number of labeled rooted connected graphs. 11
 0, 1, 2, 12, 152, 3640, 160224, 13063792, 2012388736, 596666619648, 344964885948160, 392058233038486784, 880255154481199466496, 3916538634445633156373504, 34603083354426212294072477696, 607915214065957203519146330173440 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 10, R_p. R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Problem 5.20, G(x). LINKS T. D. Noe, Table of n, a(n) for n=0..50 FORMULA E.g.f.: Sum(2^binomial(n, 2)*x^n/(n-1)!, n=1..infinity)/Sum(2^binomial(n, 2)*x^n/n!, n=0..infinity). a(n) = n * A001187(n). MAPLE add(2^binomial(n, 2)*x^n/(n-1)!, n=1..31)/add(2^binomial(n, 2)*x^n/n!, n=0..31); MATHEMATICA f[x_, lim_] := Sum[2^Binomial[n, 2]*x^n/(n - 1)!, {n, 1, lim}] / Sum[2^Binomial[n, 2]*x^n/n!, {n, 0, lim}]; nn = 15; Range[0, nn]! CoefficientList[Series[f[x, nn], {x, 0, nn}], x] (* T. D. Noe, Oct 21 2011 *) CROSSREFS Cf. A006125. Sequence in context: A000795 A085628 A177777 * A139383 A216351 A130529 Adjacent sequences:  A053546 A053547 A053548 * A053550 A053551 A053552 KEYWORD nonn AUTHOR N. J. A. Sloane, Jan 16 2000 STATUS approved

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Last modified November 21 09:20 EST 2018. Contains 317433 sequences. (Running on oeis4.)