OFFSET
0,2
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (0,2,0,-1).
FORMULA
G.f.: (1 + 2*x - x^2 - x^5) / (1 - x^2)^2.
From Colin Barker, Mar 04 2017: (Start)
a(n) = 2*a(n-2) - a(n-4) for n>3.
a(n) = 1 for n>1 and even.
a(n) = (n+5) / 2 for n>1 and odd.
(End)
PROG
(PARI) Vec((1 + 2*x - x^2 - x^5) / ((1 - x)^2*(1 + x)^2) + O(x^100)) \\ Colin Barker, Mar 04 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Mar 04 2017
STATUS
approved