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A014945 Numbers n such that n divides 4^n - 1. 19

%I

%S 1,3,9,21,27,63,81,147,171,189,243,441,513,567,657,729,903,1029,1197,

%T 1323,1539,1701,1971,2187,2667,2709,3087,3249,3591,3969,4599,4617,

%U 5103,5913,6321,6561,7077,7203,8001,8127,8379,9261,9747,10773,11907,12483

%N Numbers n such that n divides 4^n - 1.

%C This sequence is closed under multiplication. - _Charles R Greathouse IV_, Nov 03 2016

%F a(n) = A014741(n+1)/2.

%t Select[Range[12500],Divisible[4^#-1,#]&] (* _Harvey P. Dale_, Mar 23 2011 *)

%o (PARI) is(n)=Mod(4,n)^n==1 \\ _Charles R Greathouse IV_, Nov 03 2016

%K nonn

%O 1,2

%A _Olivier GĂ©rard_

%E More terms and better description from _Benoit Cloitre_, Mar 05 2002

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Last modified November 19 02:01 EST 2018. Contains 317332 sequences. (Running on oeis4.)