A016874 a(n) = (5*n + 2)^2.

4, 49, 144, 289, 484, 729, 1024, 1369, 1764, 2209, 2704, 3249, 3844, 4489, 5184, 5929, 6724, 7569, 8464, 9409, 10404, 11449, 12544, 13689, 14884, 16129, 17424, 18769, 20164, 21609, 23104, 24649, 26244

Offset

0,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..2000

Eric Weisstein's MathWorld, Polygamma Function.

Wikipedia, Polygamma Function.

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

Formula

a(n) = a(n-1) + 50*n - 5; a(0)=4. - Vincenzo Librandi, Jun 07 2011

Sum_{n>=0} 1/a(n) = polygamma(1, 2/5)/25 = 0.2910142636... - Amiram Eldar, Oct 02 2020

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). - Wesley Ivan Hurt, Oct 02 2020

G.f.: -(4+x)*(1+9*x)/(-1+x)^3. - Wesley Ivan Hurt, Oct 02 2020

Example

a(0) = (5*0 + 2)^2 = 4.

Mathematica

(5*Range[0, 40]+2)^2  (* Harvey P. Dale, Feb 19 2011 *)

Prog

(Magma) [(5*n+2)^2: n in [0..40]]; // Vincenzo Librandi, Jun 07 2011
(PARI) a(n)=(5*n+2)^2 \\ Charles R Greathouse IV, Jun 17 2017

Crossrefs

Sequence in context: A061100 A147803 A112533 * A360883 A092866 A340662

Adjacent sequences: A016871 A016872 A016873 * A016875 A016876 A016877

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved