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 A229630 #12 Oct 17 2013 01:59:36
%S A229630 4,4,4,6,6,118909855,5740959589,79235997091
%N A229630 a(n) is the smallest semiprime m such that 2*m^k-1 is prime for k = 1, 2, ..., n.
%e A229630 a(5)=6 because 2*6^k-1 is prime for k=1,2,3,4,5 and 6 is the smallest semiprime with this property. Also 6 is the smallest such number.
%t A229630 a[n_]:=(For[m=1,!(2<Length[Divisors[m]]<5&&Union[Table[PrimeQ[2m^k-1],{k,n}]]=={True}),m++];m); Do[Print[a[n]], {n,7}]
%o A229630 (PARI) \\ Code to find a(8), can be modified to find other terms easily
%o A229630 issemi(n)=bigomega(n)==2
%o A229630 is8(m)=for(i=2,8,if(!ispseudoprime(2*m^i-1),return(0)));1
%o A229630 forprime(p=2,1e12,m=(p+1)/2;if(issemi(m)&&is8(m),return(m))) \\ _Charles R Greathouse IV_, Oct 17 2013
%Y A229630 Cf. A229626, A229627, A229902.
%K A229630 nonn,more
%O A229630 1,1
%A A229630 _Farideh Firoozbakht_, Oct 14 2013
%E A229630 a(8) from _Charles R Greathouse IV_, Oct 17 2013