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 A121387 #31 Oct 28 2023 09:24:27
%S A121387 25,65,85,145,169,185,205,221,265,289,305,365,377,445,481,485,493,505,
%T A121387 533,545,565,629,685,689,697,745,785,793,841,865,901,905,949,965,985,
%U A121387 1037,1073,1145,1157,1165,1189,1205,1241,1261,1285,1313,1345,1369,1385,1405,1417
%N A121387 Semiprimes p*q with p and q primes of the form 4k+1 (A002144).
%C A121387 p and q can be the same. [_Harvey P. Dale_, Jan 15 2012]
%C A121387 The terms are semiprimes of the form 4k + 1, and comprise only a portion of all such semiprimes, see A108181. - _Richard R. Forberg_, Aug 27 2013
%H A121387 François Huppé, <a href="/A121387/b121387.txt">Table of n, a(n) for n = 1..10000</a> (First 1000 terms from T. D. Noe).
%e A121387 65 = 5 * 13. Note that 5 mod 4 = 1 and 13 mod 4 = 1, so 65 is a term.
%t A121387 With[{prs=Select[Prime[Range[150]],Mod[#,4]==1&]},Take[Union[Times @@@ Tuples[prs,2]],60]] (* _Harvey P. Dale_, Jan 15 2012 *)
%Y A121387 Cf. A001358, A002144.
%Y A121387 Fifth row of A121388.
%Y A121387 Union of A080109 and A131574.
%Y A121387 Cf. A107978, A080774, A108181.
%K A121387 easy,nonn
%O A121387 1,1
%A A121387 _Alford Arnold_, Jul 26 2006, corrected Jun 24 2007
%E A121387 Better definition from _T. D. Noe_, Sep 25 2007