A010695 Period 2: repeat (2,5).

2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5, 2, 5

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Comments

Also decimal expansion of 25/99.

Continued fraction expansion of A176052. - R. J. Mathar, Mar 08 2012

Periodic part of the partial quotients of the continued fraction expansion of sqrt(7/5), which starts [1, 5, 2, 5, 2, 5, ...]. - Hugo Pfoertner, Jan 10 2025

Links

• Index entries for linear recurrences with constant coefficients, signature (0,1).

Crossrefs

Cf. A010674 (2^(1-(-1)^n) - 1).

Cf. A010691.

Programs

Magma

&cat [[2,5]^^50]; // Bruno Berselli, Dec 29 2015

Mathematica

PadRight[{}, 100, {2, 5}] (* Paolo Xausa, Jan 16 2025 *)

Maxima

makelist(if evenp(n) then 2 else 5, n, 0, 80); /* Martin Ettl, Nov 09 2012 */

Formula

G.f.: (2+5*x)/((1-x)*(1+x)). - R. J. Mathar, Nov 21 2011

a(n) = 2^(1-(-1)^n) + 1. - Bruno Berselli, Dec 29 2015

From Nicolas Bělohoubek, Nov 11 2021: (Start)

a(n) = 10/a(n-1). See also A010691.

a(n) = 7 - a(n-1). See also A010702. (End)

Extensions

Edited by Bruno Berselli, Dec 29 2015