A216156 Period of powers of 11 mod 10^n.

10, 50, 500, 5000, 50000, 500000, 5000000, 50000000, 500000000, 5000000000, 50000000000, 500000000000, 5000000000000, 50000000000000, 500000000000000, 5000000000000000, 50000000000000000, 500000000000000000

Offset

1,1

Comments

Essentially the same as A093143. - R. J. Mathar, Sep 06 2012

Also period of squares mod 10^n. - Mohammed Yaseen, Apr 18 2023

Links

Table of n, a(n) for n=1..18.

Index entries for linear recurrences with constant coefficients, signature (10).

Formula

a(n) = 5*10^(n-1), n >= 2.

Example

a(2) = 50 because 11^50 = 11739085287969531650666649599035831993898213898723001 = 1 mod 1000.

Mathematica

Join[{10}, NestList[10*# &, 50, 20]] (* Paolo Xausa, Feb 20 2024 *)

Crossrefs

Cf. A001020, A216099.

Sequence in context: A124872 A240534 A223161 * A072296 A143558 A106041

Adjacent sequences: A216153 A216154 A216155 * A216157 A216158 A216159

Keyword

nonn,base,easy

Author

V. Raman, Sep 02 2012

Status

approved