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 A103515 #4 Mar 31 2012 10:23:47 %S A103515 5,29,419,2309,30029,1021019,19399379,892371479,51757545839, %T A103515 821495767572479,14841476269619,304250263527209, %U A103515 54873078184468933509119,2459559130353965639,521426535635040715679,15751252788463309939261439 %N A103515 Primes of the form primorial P(k)*2^n-1 with minimal n, n>=0, k>=2. %C A103515 Conjecture: sequence is defined for all k>=2 %e A103515 P(2)*2^0-1=3*2-1=5 is prime, so a(2)=5; %e A103515 P(4)*2^1-1=7*5*3*2*2-1=419 is prime, so a(4)=419; %t A103515 nmax = 2^2048; npd = 2; n = 2; npd = npd*Prime[n]; While[npd < nmax, tt = 1; cp = npd*tt - 1; While[ ! (PrimeQ[cp]), tt = tt*2; cp = npd*tt - 1]; Print[cp]; n = n + 1; npd = npd*Prime[n]] %Y A103515 Cf. A002110, A005234, A014545, A018239, A006794, A057704, A057705, A103153, A103154. %K A103515 nonn %O A103515 1,1 %A A103515 _Lei Zhou_, Feb 15 2005