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 A381465 #12 Feb 26 2025 06:28:29
%S A381465 4,9,14,15,22,34,39,49,65,69,74,82,85,86,93,94,111,133,145,158,159,
%T A381465 183,185,194,201,203,209,214,219,226,235,259,265,267,289,299,301,303,
%U A381465 319,321,323,326,327,334,341,346,358,361,362,365,371,377,386,393,403,407,413,415,422,427,437,469,471
%N A381465 Semiprimes k such that 6*k + 1 is also a semiprime.
%H A381465 Robert Israel, <a href="/A381465/b381465.txt">Table of n, a(n) for n = 1..10000</a>
%e A381465 a(3) = 14 is a term because 14 = 2 * 7 is a semiprime and 6 * 14 + 1 = 85 = 5 * 17 is also a semiprime.
%p A381465 select(t -> numtheory:-bigomega(t) = 2 and numtheory:-bigomega(6*t+1)=2, [$4..1000]);
%t A381465 s = {}; Do[If[{2, 2} == PrimeOmega[{k, 6*k + 1}], AppendTo[s, k]], {k, 1000}] ; s
%o A381465 (PARI) isok(k) = (bigomega(k)==2) && (bigomega(6*k+1)==2); \\ _Michel Marcus_, Feb 26 2025
%Y A381465 Cf. A001358, A007693, A111153, A111170.
%K A381465 nonn
%O A381465 1,1
%A A381465 _Zak Seidov_ and _Robert Israel_, Feb 24 2025