A024064 a(n) = 6^n - n^2.

1, 5, 32, 207, 1280, 7751, 46620, 279887, 1679552, 10077615, 60466076, 362796935, 2176782192, 13060693847, 78364163900, 470184984351, 2821109907200, 16926659444447, 101559956668092, 609359740010135

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..500
• Index entries for linear recurrences with constant coefficients, signature (9, -21, 19, -6).

Programs

Magma

[6^n-n^2: n in [0..25]]; // Vincenzo Librandi, Jul 03 2011

Mathematica

Table[6^n-n^2,{n,0,20}] (* or *) LinearRecurrence[{9,-21,19,-6},{1,5,32,207},20] (* Harvey P. Dale, Mar 26 2014 *)

Formula

a(0)=1, a(1)=5, a(2)=32, a(3)=207, a(n)=9*a(n-1)-21*a(n-2)+19*a(n-3)- 6*a(n-4). - Harvey P. Dale, Mar 26 2014

G.f.: (5*x^3+8*x^2-4*x+1)/((x-1)^3*(6*x-1)). - Harvey P. Dale, Mar 26 2014