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 A224081 #30 Feb 12 2023 14:25:03
%S A224081 1,4,5,6,11,12,18,39,51,98,124,170,179,208,248,838,919,939,1233,1352,
%T A224081 2177,3070,10714
%N A224081 Numbers k such that A112141(k) + 1 is prime.
%C A224081 This is the semiprime analog to A014545.
%e A224081 4*6*9*10+1 = 2161 which is prime.
%t A224081 NextSemiPrime[n_, k_: 1] := Block[{c = 0, sgn = Sign[k]}, sp = n + sgn; While[c < Abs[k], While[ PrimeOmega[sp] != 2, If[sgn < 0, sp--, sp++]]; If[sgn < 0, sp--, sp++]; c++]; sp + If[sgn < 0, 1, -1]]; f[n_] := Times @@ NestList[NextSemiPrime, 2^2, n - 1]; k = 1; lst = {}; While[k < 4651, If[ PrimeQ[f[k] + 1], Print[k]; AppendTo[lst, k]]; k++]; lst
%Y A224081 Cf. A112141, A014545, A224082.
%K A224081 nonn,more
%O A224081 1,2
%A A224081 _Jonathan Vos Post_ and _Robert G. Wilson v_, Apr 02 2013
%E A224081 a(23) from _Tyler Busby_, Feb 12 2023