A071126 Length of least repunit which is a multiple of the n-th prime, or 0 if no such multiple exists.

0, 3, 0, 6, 2, 6, 16, 18, 22, 28, 15, 3, 5, 21, 46, 13, 58, 60, 33, 35, 8, 13, 41, 44, 96, 4, 34, 53, 108, 112, 42, 130, 8, 46, 148, 75, 78, 81, 166, 43, 178, 180, 95, 192, 98, 99, 30, 222, 113, 228, 232, 7, 30, 50, 256, 262, 268, 5, 69, 28, 141, 146, 153, 155, 312, 79, 110

Offset

1,2

Comments

If prime(n) = p then a(n) is a divisor of p-1. - Amarnath Murthy, Nov 11 2002

Links

Michael De Vlieger, Table of n, a(n) for n = 1..1000

P. De Geest, Repunits and Their Factors

Amarnath Murthy, On the divisors of Smarandache Unary Sequence, Smarandache Notions Journal, Vol. 11, 2000.

A. A. A. Steward, Factorization of Repunits[up to R(196)]. Cached copy, Sep 25 2000.

Michael De Vlieger, Records and positions in first 1000 terms of A071126

Example

The 13th prime, 41, divides the repunit 11111, the smallest among all R(5k) which are multiples of 41.

Mathematica

Table[Function[p, If[Divisible[10, p], 0, k = {1}; While[! Divisible[ FromDigits@ k, p], AppendTo[k, 1]]; Length@ k]]@ Prime@ n, {n, 67}] (* Michael De Vlieger, May 20 2017 *)

Crossrefs

Number of 1's in A077573(n).

Cf. A000042. Apart from a(2), identical to A002371.

Sequence in context: A334950 A171419 A077574 * A077187 A011079 A334874

Adjacent sequences: A071123 A071124 A071125 * A071127 A071128 A071129

Keyword

nonn

Author

Lekraj Beedassy, May 28 2002

Status

approved