|
Search: id:A052621
|
|
|
| A052621 |
|
A simple regular expression in a labeled universe. |
|
+0
1
|
|
| 2, 1, 2, 6, 48, 120, 720, 5040, 80640, 362880, 3628800, 39916800, 958003200, 6227020800, 87178291200, 1307674368000, 41845579776000, 355687428096000, 6402373705728000, 121645100408832000, 4865804016353280000
(list; graph; listen)
|
|
|
OFFSET
|
0,1
|
|
|
LINKS
|
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 567
|
|
FORMULA
|
E.g.f.: -(x^3+x^2+x+2)/(-1+x^4)
Recurrence: {a(1)=1, a(3)=6, a(2)=2, a(0)=2, (-n^4-35*n^2-50*n-24-10*n^3)*a(n)+a(n+4)}
Sum(1/4*(_alpha^3+_alpha^2+2*_alpha+1)*_alpha^(-1-n), _alpha=RootOf(-1+_Z^4))*n!
2n! if n is 0 mod 4, n! otherwise.
|
|
MAPLE
|
spec := [S, {S=Union(Sequence(Z), Sequence(Prod(Z, Z, Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
|
|
CROSSREFS
|
Sequence in context: A038078 A000139 A114572 this_sequence A131057 A051852 A054495
Adjacent sequences: A052618 A052619 A052620 this_sequence A052622 A052623 A052624
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
|
|
|
Search completed in 0.002 seconds
|
