OFFSET
0,2
LINKS
Index entries for linear recurrences with constant coefficients, signature (0, 12, 0, -4).
FORMULA
a(n) = Pell(n+1)*2^[(n+1)/2]. a(n) = 12*a(n-2) - 4*a(n-4) for n>=4. G.f.: (1+4*x-2*x^2)/(1-12*x^2+4*x^4).
EXAMPLE
Sequence begins: {1*1, 2*2, 5*2, 12*4, 29*4, 70*8, 169*8, 408*16, ...}.
PROG
(PARI) a(n)=polcoeff((1+4*x-2*x^2)/(1-12*x^2+4*x^4)+x*O(x^n), n)
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Oct 25 2004
STATUS
approved