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 A067935 Let rep(n) be the n-th repunit number, sequence gives values of n such that : rep(n)==rep(2) (mod n). 1

%I

%S 1,2,4,5,10,14,20,22,25,26,34,38,44,46,50,58,62,74,82,86,94,100,106,

%T 110,118,122,134,140,142,146,158,166,178,182,185,194,202,206,214,218,

%U 220,226,254,260,262,274,278,298,302,308,314,326,334,346,350,358,362

%N Let rep(n) be the n-th repunit number, sequence gives values of n such that : rep(n)==rep(2) (mod n).

%C (10^5-1)/9 = 11+5*2220, hence 5 is in the sequence.

%H Robert Israel, <a href="/A067935/b067935.txt">Table of n, a(n) for n = 1..10000</a>

%p filter:= n -> 10&^n -100 mod (9*n) = 0:

%p select(filter, [\$1..400]); # _Robert Israel_, Jul 02 2019

%Y Cf. A002275, A095250 (rep(n) mod n).

%K nonn

%O 1,2

%A _Benoit Cloitre_, Mar 05 2002

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Last modified December 8 20:37 EST 2021. Contains 349596 sequences. (Running on oeis4.)