OFFSET
1,1
COMMENTS
Number of different coefficient values in expansion of Product_{i=1..n} (1 + q^2 + q^4 + ... + q^(2i)).
The given terms have a second difference that is periodic with the period 1, 0, 0, 1, ... of length 4, an implicit recurrence. - John W. Layman, Jan 23 2001
LINKS
Index entries for linear recurrences with constant coefficients, signature (3,-4,4,-3,1).
FORMULA
O.g.f.: -x*(2*x^4 - 4*x^3 + 4*x^2 - 3*x + 2)/((x-1)^3*(x^2+1)). - R. J. Mathar, Dec 05 2007
a(n) = A039823(n) + 1. - Bruno Berselli, Jul 25 2012
a(n) = 3*a(n-1) - 4*a(n-2) + 4*a(n-3) - 3*a(n-4) + a(n-5). - Wesley Ivan Hurt, May 08 2022
PROG
(Magma) [Floor((n^2+n+8)/4): n in [1..50]]; // Bruno Berselli, Jul 25 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved