%I #16 May 09 2018 08:18:36
%S 2,3,7,27,51,55,81,1471,1483,8668,10885,20803,32605,36391,57004,61627,
%T 88651,89731
%N Numbers n such that (n-1)*2^n+1 is prime.
%t Select[Range[200], PrimeQ[(# - 1)*2^# + 1] &] (* _G. C. Greubel_, May 08 2018 *)
%o (PARI) is(n)=ispseudoprime((n-1)<<n+1) \\ _Charles R Greathouse IV_, Jun 06 2017
%Y Cf. A029544, A002064.
%K nonn,more
%O 1,1
%A _N. J. A. Sloane_, Jan 25 2008
%E a(8)-a(14) from _Jason Earls_, Jan 29 2008
%E a(15)-a(18) from _Charles R Greathouse IV_, Oct 09 2011