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%I #9 Jun 01 2013 17:43:30
%S 2,3,7,5,11,7,29,17,19,11,23,13,53,29,31,17,137,19,1217,41,43,23,47,
%T 97,101,53,109,29,59,31,7937,257,67,137,71,37,149,1217,79,41,83,43,
%U 173,89,181,47
%N Smallest prime of form n*2^m+1, m >= 0, or 0 if no prime exists.
%C Primes arising from A040076 (or 0 if no such prime exists).
%C Or: Starting with x=n+1, the first prime created by iterating the map x-> 2*x-1. - _Kevin L. Schwartz_ and _Christian N. K. Anderson_, May 13 2013
%H R. J. Mathar, <a href="/A050921/b050921.txt">Table of n, a(n) for n = 1..382</a>
%p A050921 := proc(n)
%p for m from 0 do
%p if isprime(n*2^m+1) then
%p return n*2^m+1 ;
%p end if;
%p end do;
%p end proc; # _R. J. Mathar_, Jun 01 2013
%t Do[m = 0; While[ !PrimeQ[n*2^m + 1], m++ ]; Print[n*2^m + 1], {n, 1, 47} ]
%Y Cf. A040076, A034694, A038699.
%K nonn,easy,nice
%O 1,1
%A _N. J. A. Sloane_, Dec 30 1999
%E The next term (47*2^583 + 1) is too large to show.
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