OFFSET
1,2
COMMENTS
a(n)/a(n-1) tends to 1 as n becomes very large (of order 10^3 or more).
LINKS
Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).
FORMULA
a(n) = (2*n-2)^3 + (2*n-2) - 1.
G.f.: x*(-1 + 13*x + 25*x^2 + 11*x^3)/(1-x)^4. - Vincenzo Librandi, Mar 17 2015
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4. - Vincenzo Librandi, Mar 17 2015
EXAMPLE
a(3) = (2*3-2)^3 + (2*3-2) - 1 = 67.
MATHEMATICA
Table[(2 n - 2)^3 + (2 n - 2) - 1, {n, 30}] (* Michael De Vlieger, Mar 17 2015 *)
PROG
(PARI) a(n)=8*n^3 - 24*n^2 + 26*n - 11 \\ Charles R Greathouse IV, Mar 17 2015
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Arka Mal, Mar 08 2015
EXTENSIONS
More terms from Vincenzo Librandi, Mar 17 2015
STATUS
approved