OFFSET
1,2
LINKS
Index entries for linear recurrences with constant coefficients, signature (0,14,0,-1).
FORMULA
Recurrence: a(1)=1, a(2)=3, a(3)=14*a(1)+a(2), a(4)=14*a(2)+a(1) then a(n)=14*a(n-2)-a(n-4).
G.f.: x*(x+1)^3 / ((x^2-4*x+1)*(x^2+4*x+1)). - Corrected by Colin Barker, Apr 16 2014
EXAMPLE
12*1^2+13 = 5^2.
12*3^2+13 = 11^2.
12*17^2+13 = 59^2.
PROG
(PARI) Vec(x*(x+1)^3/((x^2-4*x+1)*(x^2+4*x+1)) + O(x^100)) \\ Colin Barker, Apr 16 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Pierre CAMI, Apr 28 2005
EXTENSIONS
Edited by Ralf Stephan, Jun 01 2007
STATUS
approved