A128053 a(n)=A128056(n)/A128055(n).

1, -3, -3, 7, 7, -9, -9, 47, 47, -123, -123, 161, 161, -843, -843, 2207, 2207, -2889, -2889, 15127, 15127, -39603, -39603, 51841, 51841, -271443, -271443, 710647, 710647, -930249, -930249, 4870847, 4870847, -12752043, -12752043

Offset

0,2

Links

Table of n, a(n) for n=0..34.

Formula

a(n)=(-1)^C(n+1,2)*(F(n-1)+F(n+1))(5/6-cos(pi*n/3)/3)(1+(-1)^n)/2+(F(n)+F(n+2))(5/6-cos(pi*(n+1)/3)/3)(1-(-1)^n)/2.

Empirical g.f.: -(x-1) * (x^10-2*x^9-5*x^8+2*x^7+9*x^6+9*x^4+2*x^3-5*x^2-2*x+1) / ((x^4+3*x^2+1)*(x^8-3*x^6+8*x^4-3*x^2+1)). - Colin Barker, Jun 27 2013

Crossrefs

Cf. A128052.

Sequence in context: A228325 A327122 A071042 * A063212 A241274 A088147

Adjacent sequences: A128050 A128051 A128052 * A128054 A128055 A128056

Keyword

easy,sign

Author

Paul Barry, Feb 13 2007

Status

approved