A262787 a(n) = 41^(2*n+1).

41, 68921, 115856201, 194754273881, 327381934393961, 550329031716248441, 925103102315013629321, 1555098314991537910888601, 2614120267500775228203738281, 4394336169668803158610484050361, 7386879101213258109624223688656841, 12417343769139486882278320020632149721

Offset: 0

Author

Vincenzo Librandi, Oct 08 2015

Keywords

• nonn
• easy

Comments

41*a(n) is a square.

Links

• G. C. Greubel, Table of n, a(n) for n = 0..250
• Index entries for linear recurrences with constant coefficients, signature (1681).

Crossrefs

Second bisection of A009985 (powers of 41).

Cf. similar sequences listed in A262715.

Programs

Magma

[41^(2*n+1): n in [0..15]];

Maple

A262787:=n->41^(2*n+1): seq(A262787(n), n=0..20); # Wesley Ivan Hurt, Dec 26 2016

Mathematica

41^Range[1, 30, 2]
NestList[1681#&,41,20] (* Harvey P. Dale, Mar 18 2025 *)

PARI

vector(20, n, n--; 41^(2*n+1)) \\ Altug Alkan, Oct 08 2015

Formula

G.f.: 41/(1 - 1681*x).

a(n) = 1681*a(n-1).