OFFSET
1,2
COMMENTS
Define a(1)=0, a(2)=8, a(3)=671, a(4)=15639, a(5)=42159, a(6)=981911, the first 6 terms found for the sequence then a(7)=57799*(2*a(3)+1)-a(2)-1, a(8)=57799*(2*a(4)+1)-a(1)-1 for n>8 a(n)=57799*(2*a(n-4)+1)-a(n-8)-1 remark:57799 = 38*39*39+1 =2*19*(39^2)+1
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,0,0,115598,-115598,0,0,-1,1).
FORMULA
G.f.: -x^2*(8*x^6+663*x^5+14968*x^4+26520*x^3+14968*x^2+663*x+8) / ((x-1)*(x^4-340*x^2+1)*(x^4+340*x^2+1)). - Colin Barker, Mar 05 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Pierre CAMI, Apr 06 2005, Apr 22 2005
EXTENSIONS
Edited by N. J. A. Sloane, Aug 29 2008 at the suggestion of R. J. Mathar
More terms (using recursive formula in comment) from Jon E. Schoenfield, Jul 10 2010
a(18) from Colin Barker, Mar 05 2013
STATUS
approved