OFFSET
1,2
LINKS
Clark Kimberling, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).
FORMULA
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4).
G.f.: x*(1 + 7*x + 4*x^2)/(1 - x)^4.
MATHEMATICA
(See A213771.)
PROG
(PARI) a(n) = (4*n^3-3*n^2+n)/2; \\ Altug Alkan, Dec 16 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jul 04 2012
STATUS
approved