OFFSET
1,4
FORMULA
a(2n+2) = n+1, a(4n+1) = 4n+1, a(4n+3) = n+1. - Ralf Stephan, Jun 10 2005
Empirical g.f.: x*(x^5+3*x^4+2*x^3+x^2+x+1) / ((x-1)^2*(x+1)^2*(x^2+1)^2). [Colin Barker, Feb 18 2013]
From Luce ETIENNE, Feb 01 2017 : (Start)
a(n) = 2*a(n-4)-a(n-8).
a(n) = (9*n+1-(n+1)*(-1)^n+(3*n-1)*((-1)^((2*n-1+(-1)^n)/4)-(-1)^((2*n+1-(-1)^n)/4)))/16.
a(n) = (9*n+1-(n+1)*cos(n*Pi)+2*(3*n-1)*sin(n*Pi/2))/16. (End)
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Oct 28 2001
STATUS
approved