A072996 Coefficient of the highest power of q in the expansion of nu(0)=1, nu(1)=b and for n>=2, nu(n)=b*nu(n-1)+lambda*(n-1)_q*nu(n-2) with (b,lambda)=(2,1), where (n)_q=(1+q+...+q^(n-1)) and q is a root of unity.

1, 1, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5

Offset

0,3

Comments

Instead of listing the coefficients of the highest power of q in each nu(n), if we list the coefficients of the smallest power of q (i.e., constant terms), we get a weighted Fibonacci numbers described by f(0)=1, f(1)=1, for n>=2, f(n)=2f(n-1)+f(n-2).

Links

Table of n, a(n) for n=0..104.

M. Beattie, S. Dăscălescu and S. Raianu, Lifting of Nichols Algebras of Type B_2, arXiv:math/0204075 [math.QA], 2002.

Formula

For given b and lambda, the recurrence relation is given by; t(0)=1, t(1)=b, t(2)=b^2+lambda and for n>=3, t(n)=lambda*t(n-2).

O.g.f.: -(x+1+4*x^2)/((x-1)*(x+1)) = -4-3/(x-1)+2/(x+1). - R. J. Mathar, Dec 05 2007

Example

nu(0)=1, nu(1)=2, nu(2)=5, nu(3)=12+2q, nu(4)=29+9q+5q^2, nu(5)=70+32q+24q^2+14q^3+2q^4, nu(6)=169+102q+91q^2+42q^3+38q^4+9q^5+5q^6. By listing the coefficients of the highest power in each nu(n) we get 1,2,5,2,5,2,5,...

Crossrefs

Cf. A000129.

Sequence in context: A111129 A168464 A059688 * A244892 A278066 A153107

Adjacent sequences: A072993 A072994 A072995 * A072997 A072998 A072999

Keyword

nonn

Author

Y. Kelly Itakura (yitkr(AT)mta.ca), Aug 21 2002

Status

approved