A017390 a(n) = (11*n)^2.

0, 121, 484, 1089, 1936, 3025, 4356, 5929, 7744, 9801, 12100, 14641, 17424, 20449, 23716, 27225, 30976, 34969, 39204, 43681, 48400, 53361, 58564, 64009, 69696, 75625, 81796, 88209, 94864, 101761

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

From Amiram Eldar, Jan 25 2021: (Start)

Sum_{n>=1} 1/a(n) = Pi^2/726.

Sum_{n>=1} (-1)^(n+1)/a(n) = Pi^2/1452.

Product_{n>=1} (1 + 1/a(n)) = sinh(Pi/11)/(Pi/11).

Product_{n>=1} (1 - 1/a(n)) = sin(Pi/11)/(Pi/11). (End)

G.f.: -((121*x*(1+x))/(-1+x)^3). - Harvey P. Dale, Nov 04 2021

Mathematica

(11 Range[0, 30])^2 (* or *) LinearRecurrence[{3, -3, 1}, {0, 121, 484}, 30] (* Harvey P. Dale, Nov 04 2021 *)

Prog

(Magma) [(11*n)^2: n in [0..40]]; // Vincenzo Librandi, Sep 02 2011
(PARI) a(n)=(11*n)^2 \\ Charles R Greathouse IV, Jun 17 2017

Crossrefs

Sequence in context: A036304 A052082 A062555 * A110722 A236181 A077432

Adjacent sequences: A017387 A017388 A017389 * A017391 A017392 A017393

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved