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 A244859 Least positive multiple of n which when written in base 10 is either a repunit or of the form 1111....0000. 2

%I

%S 0,1,10,111,100,10,1110,111111,1000,111111111,10,11,11100,111111,

%T 1111110,1110,10000,1111111111111111,1111111110,111111111111111111,

%U 100,111111,110,1111111111111111111111,111000,100

%N Least positive multiple of n which when written in base 10 is either a repunit or of the form 1111....0000.

%H Robert Israel, <a href="/A244859/b244859.txt">Table of n, a(n) for n = 0..936</a> (n = 0..100 from Chai Wah Wu).

%H Chai Wah Wu, <a href="http://www.jstor.org/stable/10.4169/amer.math.monthly.121.06.529">Pigeonholes and repunits</a>, Amer. Math. Monthly, 121 (2014), 529-533.

%p A244859:= proc(n) local m,d2,d5;

%p m:= n/2^d2/5^d5;

%p 10^max(d2,d5)*(10^numtheory:-order(10,9*m)-1)/9

%p end proc:

%p A244859(0):= 0:

%p seq(A244859(n),n= 0..100); # _Robert Israel_, Jul 08 2014

%Y Equal to A004290 for the first 7 terms.

%K nonn,base

%O 0,3

%A _Chai Wah Wu_, Jul 07 2014

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Last modified October 16 23:30 EDT 2019. Contains 328103 sequences. (Running on oeis4.)