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 A140745 #13 Jul 14 2025 14:30:40
%S A140745 2,11,29,157,113,223,491,431,397
%N A140745 Smallest prime p such that the Mersenne number A000225(p) = 2^p - 1 has exactly n prime factors (counted with multiplicity).
%D A140745 J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 223, pp 63-4, Ellipse Paris 2008.
%t A140745 a[n_]:=Module[{p=0},Until[PrimeOmega[2^Prime[p]-1]==n,p++];Prime[p]];Array[a,6] (* _James C. McMahon_, Jul 14 2025 *)
%o A140745 (PARI) a(n) = forprime(p=2, oo, if(bigomega(2^p-1)==n, return(p))); \\ _Jinyuan Wang_, Aug 10 2021
%Y A140745 Cf. A000225, A001222, A046051, A136033.
%K A140745 nonn,more
%O A140745 1,1
%A A140745 _Lekraj Beedassy_, Jul 12 2008