The On-Line Encyclopedia of Integer Sequences (OEIS)

A052710 revision #1

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,6

LINKS

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

ECS 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)}, unlabelled]: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,new

AUTHOR

encyclopedia@pommard.inria.fr, Jan 25 2000

STATUS

approved