OFFSET
0,3
LINKS
Index entries for linear recurrences with constant coefficients, signature (2,1,2,-1).
FORMULA
a(n) = 2*a(n-1) + a(n-2) + 2*a(n-3) - a(n-4).
a(n) = Sum_{k=0..floor(n/2)} binomial(2*n-2*k+1,2*k).
PROG
(PARI) my(N=30, x='x+O('x^N)); Vec((1-x+x^2)/((1-x+x^2)^2-4*x^2))
(PARI) a(n) = sum(k=0, n\2, binomial(2*n-2*k+1, 2*k));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Oct 02 2024
STATUS
approved