login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 16 13:12 EDT 2018. Contains 316263 sequences. (Running on oeis4.)