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!)
A052606 E.g.f. (1-x)^2/(1-4x+x^2). 0
1, 2, 16, 180, 2688, 50160, 1123200, 29342880, 876072960, 29425939200, 1098191001600, 45083550758400, 2019049224192000, 97957525739673600, 5118154482618777600, 286518188551795200000, 17108806991486386176000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..16.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 551

FORMULA

E.g.f.: (-1+x)^2/(1-4*x+x^2)

Recurrence: {a(0)=1, a(1)=2, (n^2+3*n+2)*a(n)+(-4*n-8)*a(n+1)+a(n+2)=0, a(2)=16}

Sum(-1/3*(-1+2*_alpha)*_alpha^(-1-n), _alpha=RootOf(1-4*_Z+_Z^2))*n!

MAPLE

spec := [S, {S=Sequence(Prod(Sequence(Z), Sequence(Z), Union(Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);

CROSSREFS

Sequence in context: A138014 A206988 A217360 * A011553 A291816 A123898

Adjacent sequences:  A052603 A052604 A052605 * A052607 A052608 A052609

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 | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 20 23:24 EDT 2021. Contains 345312 sequences. (Running on oeis4.)