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%I #8 Jun 15 2017 11:30:21
%S 23,89,353,1409,5767169,23068673,96757023244289,
%T 26596368031521841843535873,467888254516290387262140085218681290753,
%U 1871553018065161549048560340874725163009,9050275065266633231852330504065427777405047260984689248417349633
%N Primes of form 11*2^n+1.
%t Select[11*2^Range[210]+1,PrimeQ] (* _Harvey P. Dale_, Jun 15 2017 *)
%Y For more terms see A002261.
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Dec 29 1999