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

Author

Paul Curtz, Nov 09 2008

Keywords

• nonn
• easy

Comments

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

Links

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

Crossrefs

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

Programs

Mathematica

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

PARI

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

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)

Extensions

More terms from Vincenzo Librandi, Nov 26 2010