login
A289443
a(0) = 2, a(1) = 6; thereafter a(n) = 3*n^2.
1
2, 6, 12, 27, 48, 75, 108, 147, 192, 243, 300, 363, 432, 507, 588, 675, 768, 867, 972, 1083, 1200, 1323, 1452, 1587, 1728, 1875, 2028, 2187, 2352, 2523, 2700, 2883, 3072, 3267, 3468, 3675, 3888, 4107, 4332, 4563, 4800, 5043, 5292, 5547, 5808, 6075, 6348, 6627, 6912, 7203, 7500
OFFSET
0,1
FORMULA
G.f.: (2 + 7*x^3 - 3*x^4)/(1 - x)^3. - Vincenzo Librandi, Jul 08 2017
E.g.f.: 2 + 3*x + 3*exp(x)*x*(1 + x). - Stefano Spezia, Dec 17 2022
MATHEMATICA
Join[{2, 6}, Table[3 n^2, {n, 2, 50}]] (* or *) {2, 6}~Join~LinearRecurrence[{3, -3, 1}, {12, 27, 48}, 50] (* Vincenzo Librandi, Jul 08 2017 *)
PROG
(Magma) [2, 6] cat [3*n^2: n in [2..60]]; // Vincenzo Librandi, Jul 08 2017
(PARI) a(n)=3*n^2+if(n<2, n+2) \\ Charles R Greathouse IV, Oct 21 2022
CROSSREFS
Essentially the same as A033428.
Sequence in context: A350294 A052971 A364423 * A029863 A091919 A059078
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jul 07 2017
STATUS
approved