%I #27 Mar 01 2022 07:26:08

%S 47,67,2731,2887,5827,13567,41647,44851,46051,47911,59671,61231,66571,

%T 78439,90107,109891,138007,141067,144451,164011,183907,321091,406591,

%U 430987,460531,501187,513731,532027,537587,554731,598687,673207,677447

%N Numbers n of the form 4*k+3 such that 2^(m-1) == 1 (mod m) where m = (2*n-1)*n.

%C The first composite is 45812984491. [_Charles R Greathouse IV_, Mar 20 2011]

%t Select[4*Range[200000]+3,PowerMod[2,(2#-1)#-1,#(2#-1)]==1&] (* _Harvey P. Dale_, Mar 01 2017 *)

%Y Subsequence of A004767 (4*k+3).

%K nonn

%O 1,1

%A _Alzhekeyev Ascar M_, Mar 16 2011