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 A198327 #29 Feb 16 2025 08:33:15
%S A198327 6,35,51,57,87,93,95,121,123,143,145,161,185,187,203,205,215,217,219,
%T A198327 221,237,249,267,289,291,301,303,305,321,323,329,341,393,395,413,415,
%U A198327 417,447,453,471,473,517,519,529,535,537,545,553,581,583,591,635,669,671
%N A198327 Semiprimes k such that k-2 is also a semiprime.
%C A198327 Omega(a(n)) = Omega(a(n) - Omega(a(n))) because Omega(a(n)) = 2, and a(n) - 2 is semiprime => this sequence is a subsequence of A200925.
%H A198327 Harvey P. Dale, <a href="/A198327/b198327.txt">Table of n, a(n) for n = 1..1000</a>
%H A198327 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Semiprime.html">Semiprime</a>
%F A198327 a(n) = A092207(n) + 2.
%t A198327 PrimeFactorExponentsAdded[n_] := Plus @@ Flatten[Table[ #[[2]], {1}] & /@ FactorInteger[n]]; Select[ Range[ 671], PrimeFactorExponentsAdded[ # ] == PrimeFactorExponentsAdded[ # - 2] == 2 &]
%t A198327 SemiPrimeQ[n_Integer] := If[Abs[n] < 2, False, (2 == Plus @@ Transpose[FactorInteger[Abs[n]]][[2]])]; Select[Range[1000], SemiPrimeQ[#] && SemiPrimeQ[# - 2] &] (* _T. D. Noe_, Nov 27 2011 *)
%t A198327 #[[3,1]]&/@Select[Partition[Table[{n,PrimeOmega[n]},{n,700}],3,1], #[[1,2]]==#[[3,2]]==2&] (* _Harvey P. Dale_, Dec 10 2011 *)
%Y A198327 Cf. A001222, A092207, A200925.
%K A198327 nonn
%O A198327 1,1
%A A198327 _Michel Lagneau_, Nov 25 2011