A147651 First trisection of A028560.

0, 27, 72, 135, 216, 315, 432, 567, 720, 891, 1080, 1287, 1512, 1755, 2016, 2295, 2592, 2907, 3240, 3591, 3960, 4347, 4752, 5175, 5616, 6075, 6552, 7047, 7560, 8091, 8640, 9207, 9792, 10395, 11016

Offset

0,2

Comments

Nonnegative k such that k/9 + 1 is a square. - Bruno Berselli, Apr 10 2018

Links

Table of n, a(n) for n=0..34.

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

Formula

a(n) = 9*n*(n+2).

a(n) = a(n-1) + 9*A144396(n) for n > 0.

From Elmo R. Oliveira, Nov 29 2024: (Start)

G.f.: 9*x*(3 - x)/(1-x)^3.

E.g.f.: 9*x*(3 + x)*exp(x).

a(n) = 9*A005563(n) = 3*A067725(n) = A028560(3*n).

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n >= 3. (End)

Mathematica

Table[9 n (n + 2), {n, 0, 40}]  (* Harvey P. Dale, Feb 20 2011 *)

Prog

(PARI) a(n)=9*n*(n+2) \\ Charles R Greathouse IV, Jun 17 2017

Crossrefs

Cf. A005563, A028560, A067725, A144396, A144454.

Sequence in context: A039414 A043237 A044017 * A325824 A163506 A226357

Adjacent sequences: A147648 A147649 A147650 * A147652 A147653 A147654

Keyword

nonn,easy

Author

Paul Curtz, Nov 09 2008

Extensions

More terms from Vincenzo Librandi, Nov 26 2010

Status

approved