OFFSET
0,6
FORMULA
O.g.f.: (x^2+x+1)*x^3/((x-1)^2*(1+x)^2*(1+x^2)). - R. J. Mathar, Jul 07 2008
a(n) = Sum_{i=1..floor(n/2)} sign((n-2i) mod 4). - Wesley Ivan Hurt, Apr 10 2018
a(n) = A106466(n-3) for n>=3. - Georg Fischer, Oct 07 2018
MAPLE
a := n -> A005044(n+2) - A005044(n-7): A005044 := n -> floor((1/48)*(n^2 + 3*n + 21 + (-1)^(n-1)*3*n)): seq(a(n), n=0..79); # Johannes W. Meijer, Oct 08 2013
MATHEMATICA
Table[Sum[Sign[Mod[n - 2 i, 4]], {i, Floor[n/2]}], {n, 0, 100}] (* Wesley Ivan Hurt, Apr 10 2018 *)
PROG
(PARI) a(n) = if(n%2, n\2, n\4); \\ Altug Alkan, Apr 16 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paul Curtz, Aug 16 2007
EXTENSIONS
Edited by R. J. Mathar, Jul 07 2008
STATUS
approved