%I
%S 0,0,0,1,0,1,2,5,0,5,2,1,4,3,6,11,0,19,14,3,2,5,2,3,16,11,66,35,4,7,
%T 122,17,14,13,2,3,4,15,34,52519,4,3,22,29,10,29,6,1,4,5,38
%N Least m such that 2^n+5^m is prime.
%C a(51) > 10^5
%e a(0)=0 because 2^0+5^0=1+1=2 is prime.
%t f[n_] := Block[{p = If[n < 3  EvenQ@n, 0, 1]}, While[ !PrimeQ[5^p + 2^n ], p += 2 ]; p] ; Table[f@n, {n, 0, 38}] (* _Robert G. Wilson v_ *)
%o (PARI) for(n=0,38,k=2^n;m=0;while(!isprime(k+5^m),m++);print1(m,","))  (Klaus Brockhaus, Oct 15 2006)
%Y Cf. A123252.
%K nonn,hard,more
%O 0,7
%A _Zak Seidov_, Oct 11 2006
%E Entries through a(38) checked by _Klaus Brockhaus_, Oct 15 2006
%E a(40)a(50) from _Robert G. Wilson v_, Nov 14 2006
%E a(39)=52519 from _Max Alekseyev_, Mar 15 2011
