login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A054948 Number of labeled semi-strong digraphs on n nodes. 3
1, 1, 2, 22, 1688, 573496, 738218192, 3528260038192, 63547436065854848, 4400982906402148836736, 1190477715153930158152163072, 1270476960212865235273469079407872, 5381083212549793228422395071641588743168, 90765858793484859057065439213726376149311958016 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..13.

V. A. Liskovets, Some easily derivable sequences, J. Integer Sequences, 3 (2000), #00.2.2.

FORMULA

E.g.f.: 1/(1-B(x)) where B(x) is e.g.f. for A054947. - Vladeta Jovovic, Mar 11 2003

E.g.f. A(x) satisfies: Sum_{n>=0} 2^(n^2-n)*x^n/n! / A(2^n*x) = 1. - Paul D. Hanna, Oct 27 2012

MATHEMATICA

a[n_] := a[n] = Module[{A}, A = 1+Sum[a[k]*x^k/k!, {k, 1, n-1}]; n!*SeriesCoefficient[Sum[2^(k^2-k)*x^k/k!/(A /. x -> 2^k*x) , {k, 0, n}], {x, 0, n}]]; a[0]=1; Table[a[n], {n, 0, 13}] (* Jean-Fran├žois Alcover, Dec 15 2014, after Paul D. Hanna *)

PROG

(PARI) a(n)=local(A=1+sum(k=1, n-1, a(k)*x^k/k!)+x*O(x^n)); n!*polcoeff(sum(k=0, n, 2^(k^2-k)*x^k/k!/subst(A, x, 2^k*x)), n)

for(n=0, 10, print1(a(n), ", ")) \\ Paul D. Hanna, Oct 27 2012

CROSSREFS

Cf. A054947, A218393.

Sequence in context: A177410 A193486 A337577 * A330124 A104149 A113761

Adjacent sequences:  A054945 A054946 A054947 * A054949 A054950 A054951

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, May 24 2000

EXTENSIONS

More terms from Vladeta Jovovic, Mar 11 2003

Changed offset to 0 and added a(0)=1 by Paul D. Hanna, Oct 27 2012

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 9 05:11 EDT 2021. Contains 343688 sequences. (Running on oeis4.)