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 A379407 #13 Jan 12 2025 21:05:59
%S A379407 4,9,33,213,2315,30031,510515,9699691,223092871,6469693233,
%T A379407 200560490134,7420738134814,304250263527221,13082761331670031,
%U A379407 614889782588491414,32589158477190044737,1922760350154212639074,117288381359406970983271,7858321551080267055879091
%N A379407 a(n) is the smallest semiprime > primorial(n).
%F A379407 a(n) = A106325(A002110(n)+1).
%e A379407 primorial(2) = 2*3 = 6 so a(2) = 9 because 9 = 3*3 is next semiprime > 6.
%t A379407 a[n_] := Module[{m = Times @@ Prime[Range[n]] + 1}, While[PrimeOmega[m] != 2, m++]; m]; Array[a, 20] (* _Amiram Eldar_, Jan 01 2025 *)
%o A379407 (Python)
%o A379407 import sympy
%o A379407 def ok(n): return sum(sympy.factorint(n).values()) == 2
%o A379407 primorial = 1
%o A379407 l = []
%o A379407 for i in range(1,20):
%o A379407 primorial *= sympy.prime(i)
%o A379407 next_sp = primorial + 1
%o A379407 while not(ok(next_sp)):
%o A379407 next_sp += 1
%o A379407 l.append(next_sp)
%o A379407 print(l)
%Y A379407 Cf. A001358, A002110, A089539, A106325.
%K A379407 nonn
%O A379407 1,1
%A A379407 _Alexandre Herrera_, Dec 22 2024