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 A103782 #4 Mar 31 2012 10:23:47 %S A103782 0,0,1,0,0,1,1,2,3,12,1,0,22,2,4,13,12,6,1,4,1,4,0,2,9,5,6,2,1,9,17, %T A103782 22,7,19,73,23,12,5,27,33,64,33,5,7,41,44,35,29,3,19,6,26,5,11,9,33, %U A103782 34,16,63,46,8,4,24,48,0,11,0,26,6,25,17,31,6,46,33,46,17,8,61,12,23,76,20,17 %N A103782 a(n) = minimal m >= 0 that makes primorial P(n)*2^m-1 prime. %C A103782 The values of n in A103515 %e A103782 P(2)*2^0-1=5 is prime, so a(2)=0; P(9)*2^2-1=892371479 is prime, so a(9)=2; %t A103782 nmax = 2^2048; npd = 2; n = 2; npd = npd*Prime[n]; While[npd < nmax, tn = 0; tt = 1; cp = npd*tt - 1; While[(cp > 1) && (! (PrimeQ[cp])), tn = tn + 1; tt = tt*2; cp = npd*tt - 1]; Print[tn]; n = n + 1; npd = npd*Prime[n]] %Y A103782 Cf. A002110, A005234, A014545, A018239, A006794, A057704, A057705, A103513, A103515. %K A103782 nonn %O A103782 2,8 %A A103782 _Lei Zhou_, Feb 15 2005