OFFSET
0,2
FORMULA
a(n) = n*(1+3*n+6*n^2)/2. a(n) = n*A085473(n)/2. a(n) = n*[C(2n+3,3)-C(2n,3)]/2. - Jonathan Vos Post, Mar 10 2006
a(0) = 0, a(1) = 5, a(2) = 31, a>2: a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + 18; G.f. = (5*x+11*x^2+2*x^3)/(1-x)^4 - Zak Seidov, Mar 10 2006
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Mar 09 2006
STATUS
approved