The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A052647 E.g.f. (2-2x-x^2)/((1-2x)(1-x^2)). 0
 2, 2, 10, 48, 408, 3840, 46800, 645120, 10362240, 185794560, 3719520000, 81749606400, 1962469555200, 51011754393600, 1428416301312000, 42849873690624000, 1371216880889856000, 46620662575398912000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS Table of n, a(n) for n=0..17. INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 593 FORMULA E.g.f.: -(-2+x^2+2*x)/(-1+2*x)/(-1+x^2) Recurrence: {a(1)=2, a(2)=10, a(0)=2, (12+2*n^3+12*n^2+22*n)*a(n)+(-n^2-5*n-6)*a(n+1)+(-2*n-6)*a(n+2)+a(n+3)=0} (2^n+Sum(1/2*_alpha^(-n), _alpha=RootOf(-1+_Z^2)))*n! n!*[2^n+(n mod 2)]. a(n) = n!*A052531(n). - R. J. Mathar, Nov 27 2011 MAPLE spec := [S, {S=Union(Sequence(Prod(Z, Z)), Sequence(Union(Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20); CROSSREFS Sequence in context: A300641 A078433 A059494 * A326983 A232974 A181334 Adjacent sequences: A052644 A052645 A052646 * A052648 A052649 A052650 KEYWORD easy,nonn AUTHOR encyclopedia(AT)pommard.inria.fr, Jan 25 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 25 15:58 EDT 2024. Contains 372800 sequences. (Running on oeis4.)