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%I #27 Nov 01 2018 21:36:09
%S 1,3,7,237,1885,51381,75765
%N Numbers k such that 2^(k-1) + k is prime.
%C No other terms below 300000. - _Giovanni Resta_, Nov 12 2012
%C a(8) > 500000. - _Robert Price_, May 24 2014
%D J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 237, p. 66, Ellipses, Paris 2008.
%H K. S. Brown, <a href="http://www.mathpages.com/home/kmath006/kmath006.htm">The Sum of the Prime Factors of N</a>. MathPages.com
%o (PARI) is(n)=isprime(2^(n-1)+n) \\ _Charles R Greathouse IV_, May 22 2017
%Y Cf. A061421.
%Y Equals A100359(n) + 1.
%K hard,nonn
%O 1,2
%A _Jason Earls_, May 02 2001
%E H. Zeisel found the probable prime 1885. - _Benoit Cloitre_, Jun 03 2002
%E New term 51381 from Nuutti Kuosa (see MathPages link). - _Max Alekseyev_, Feb 08 2009
%E Deleted an incorrect conjecture. - _N. J. A. Sloane_, Dec 27 2009
%E a(7) from _Giovanni Resta_, Nov 12 2012
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