OFFSET
0,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 1062
Index entries for linear recurrences with constant coefficients, signature (2,2,-1,-1)
FORMULA
G.f.: -(-1+x^2)/(1-2*x-2*x^2+x^3+x^4)
Recurrence: {a(0)=1, a(1)=2, a(2)=5, a(3)=13, a(n)+a(n+1)-2*a(n+2)-2*a(n+3)+a(n+4)}
Sum(-1/331*(-49-147*_alpha+25*_alpha^2+76*_alpha^3)*_alpha^(-1-n), _alpha=RootOf(1-2*_Z-2*_Z^2+_Z^3+_Z^4))
MAPLE
spec := [S, {S=Sequence(Union(Prod(Union(Sequence(Prod(Z, Z)), Z), Z), Z))}, unlabeled ]: seq(combstruct[count ](spec, size=n), n=0..20);
MATHEMATICA
CoefficientList[Series[(1-x^2)/(1-2x-2x^2+x^3+x^4), {x, 0, 30}], x] (* or *) LinearRecurrence[{2, 2, -1, -1}, {1, 2, 5, 13}, 30] (* Harvey P. Dale, Sep 21 2016 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
EXTENSIONS
More terms from James A. Sellers, Jun 05 2000
STATUS
approved