OFFSET
2,1
FORMULA
a(n)=(n + 2)*(n^2 + 10*n + 15)/12 - 0.375 + 0.125*( - 1)^n - 0.25*cos(n*Pi/2) [From Richard Choulet, Dec 13 2008]
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved