A052710 A simple context-free grammar.

0, 0, 0, 0, 1, 4, 14, 52, 201, 792, 3168, 12844, 52676, 218148, 910996, 3832072, 16222352, 69061200, 295477550, 1269863304, 5479456290

Offset

0,6

Links

Table of n, a(n) for n=0..20.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 665

Formula

G.f.: RootOf(-_Z+_Z^4+_Z^2+x)-RootOf(-_Z+_Z^4+_Z^2+x)^2-x

Recurrence: {a(1)=0, a(2)=0, a(4)=1, a(3)=0, a(5)=4, a(6)=14, (2304-4608*n-36864*n^2+73728*n^3)*a(n)+(46368+121536*n+59904*n^2-9216*n^3)*a(n+1)+(-79800-56512*n+59520*n^2+34048*n^3)*a(n+2)+(200516*n+185964+68544*n^2+7456*n^3)*a(n+3)+(-15024*n^2-22732*n+6864-2228*n^3)*a(n+4)+(-217*n^3-2604*n^2-10199*n-13020)*a(n+5)}

Maple

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

Crossrefs

Sequence in context: A244898 A244935 A199698 * A364410 A262594 A345242

Adjacent sequences: A052707 A052708 A052709 * A052711 A052712 A052713

Keyword

easy,nonn

Author

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

Status

approved