A017270 a(n) = (10*n)^2.

0, 100, 400, 900, 1600, 2500, 3600, 4900, 6400, 8100, 10000, 12100, 14400, 16900, 19600, 22500, 25600, 28900, 32400, 36100, 40000, 44100, 48400, 52900, 57600, 62500, 67600, 72900, 78400, 84100

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..10000

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

Formula

a(n) = a(n-1)+200n-100, n>0 ; a(0)=0. - Miquel Cerda, Oct 30 2016

G.f.: 100*x*(1 + x)/(1 - x)^3. - Ilya Gutkovskiy, Oct 30 2016

a(n) = 100*A000290(n). - Michel Marcus, Oct 30 2016

From Amiram Eldar, Jan 25 2021: (Start)

Sum_{n>=1} 1/a(n) = Pi^2/600.

Sum_{n>=1} (-1)^(n+1)/a(n) = Pi^2/1200.

Product_{n>=1} (1 + 1/a(n)) = sinh(Pi/10)/(Pi/10).

Product_{n>=1} (1 - 1/a(n)) = sin(Pi/10)/(Pi/10) = 5*(sqrt(5)-1)/(2*Pi). (End)

Mathematica

LinearRecurrence[{3, -3, 1}, {0, 100, 400}, 40] (* Harvey P. Dale, Oct 02 2017 *)

Prog

(Magma) [(10*n)^2: n in [0..40]]; // Vincenzo Librandi, Jul 28 2011
(PARI) a(n)=(10*n)^2 \\ Charles R Greathouse IV, Jun 17 2017

Crossrefs

Cf. A000290.

Sequence in context: A202334 A250806 A250853 * A105089 A334707 A017510

Adjacent sequences: A017267 A017268 A017269 * A017271 A017272 A017273

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved