OFFSET
1,2
LINKS
Clark Kimberling, Table of n, a(n) for n = 1..500
Index entries for linear recurrences with constant coefficients, signature (2,2,-6,0,6,-2,-2,1).
FORMULA
a(n) = (n + 1)*(n + 2)*(3 - 3*(-1)^n + 8*n + 2*n^2)/96.
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5).
G.f.: f(x)/g(x), where f(x) = x*(1 + x + 2*x^2) and g(x) = (1+x)^3*(1-x)^5.
MATHEMATICA
(See A213849.)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jul 05 2012
STATUS
approved