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 A229627 #29 Jun 14 2025 01:49:15
%S A229627 2,2,3,92581,385939,464938699,24137752519,1095265755949
%N A229627 a(n) is the smallest prime q such that 2*q^k - 1 is prime for k = 1, 2, ..., n.
%C A229627 The prime number 2 in the definition is used because 2 is the only prime p such that p*q^k - 1 can be prime for more than one prime q.
%C A229627 a(9) > 3*10^13. - _Tyler Busby_, Jan 14 2023
%t A229627 a[1]=2;a[n_]:=a[n]=(For[m=PrimePi[a[n-1]],Union[Table[PrimeQ[2 Prime[m]^k-1],{k,n}]]!={True},m++];Prime[m])
%o A229627 (PARI) a(n)=forprime(m=2,,for(k=1,n,if(!ispseudoprime(2*m^k-1), next(2))); return(m)) \\ _Charles R Greathouse IV_, Oct 01 2013
%Y A229627 Cf. A005382, A106483, A177104, A182785, A309855, A229626.
%K A229627 nonn,more
%O A229627 1,1
%A A229627 _Farideh Firoozbakht_, Sep 27 2013
%E A229627 a(7) from _Giovanni Resta_, Oct 01 2013
%E A229627 a(8) from _Tyler Busby_, Jan 06 2023