OFFSET
1,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..5000
FORMULA
a(n) = (1/3)*n*(17*n^2 - 18*n + 4).
G.f.: x*(1 + 20*x + 13*x^2)/(1-x)^4. - Colin Barker, Feb 12 2012
PROG
(Magma) [(1/6)*(34*n^3-36*n^2+8*n): n in [1..40]]; // Vincenzo Librandi, Jul 19 2011
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
James A. Record (james.record(AT)gmail.com), Nov 07 2004
STATUS
approved