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 A103513 #4 Mar 31 2012 10:23:47 %S A103513 2,13,103,1153,15013,255253,4849843,111546433,3234846607,100280245063, %T A103513 3710369067401,152125131763603,6541380632280583,307444891294245701, %U A103513 16294579238595022363,961380175077106319471,58644190679703485491571 %N A103513 Primes of the form primorial(P(k))/2-2^n with minimal n, n>=0, k>=2. %C A103513 The Mathematica Program does not produce a(2). Conjecture: sequence is defined for all k>=2. %e A103513 P(2)/2=3, 3-2^0=2 is prime, so a(2)=2; %e A103513 P(5)/2=1155, 1155-2^1=1153 is prime, so a(5)=1153; %t A103513 nmax = 2^8192; npd = 1; n = 2; npd = npd*Prime[n]; While[npd < nmax, tt = 2; cp = npd - tt; While[(cp > 1) && (! (PrimeQ[cp])), tt = tt*2; cp = npd - tt]; If[cp < 2, Print["*"], Print[cp]]; n = n + 1; npd = npd*Prime[n]] %Y A103513 Cf. A002110, A005234, A014545, A018239, A006794, A057704, A057705, A103154. %K A103513 nonn %O A103513 1,1 %A A103513 _Lei Zhou_, Feb 15 2005