This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A139457 #8 Apr 28 2015 17:19:15
%S A139457 0,1,1,1,3,1,2,4,3,1,1,1,4,10,1,11,1,2,11,14,2,8,7,3,4,4,26,21,1,4,15,
%T A139457 10,8,4,16,29,10,3,51,17,5,12,12,48,13,45,12,1,20,17,65,12,8,95,5,12,
%U A139457 11,8,110,38,28,8,1,23,13,5,7,11,21,2,20,32,9,66,4,2,1,20,34,97,28,80
%N A139457 a(n)= smallest m such that primorial(n)/2 + 2^m is prime.
%t A139457 k = 1/2; a = {}; Do[k = k*Prime[n]; m = 0; While[ ! PrimeQ[k + 2^m], m++ ]; Print[m]; AppendTo[a, m], {n, 100}]; a
%o A139457 (PARI) a(n)=my(t=prod(i=2,n,prime(i)),m); while(!isprime(t+2^m), m++); m \\ _Charles R Greathouse IV_, Apr 28 2015
%Y A139457 Cf. A067026, A067027, A139439-A139457, A103514.
%K A139457 nonn
%O A139457 1,5
%A A139457 _Artur Jasinski_, Apr 21 2008
%E A139457 a(1)=0 inserted and program corrected by _Ray Chandler_, Jun 16 2013