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 A238605 #8 Oct 17 2021 16:02:23 %S A238605 15,35,39,55,87,155,183,203,219,247,259,295,327,339,371,471,515,535, %T A238605 579,583,635,707,731,803,807,835,851,871,939,995,1011,1047,1059,1067, %U A238605 1111,1147,1191,1195,1203,1207,1211,1219,1255,1315,1339,1355,1363,1383,1507,1527,1563,1591,1643,1651,1687,1707 %N A238605 Semiprimes n such that (n+1)/4 also is a semiprime. %C A238605 A subsequence of Ruth-Aaron numbers A039752. The terms are by definition of the form n = 4k+3. %H A238605 Harvey P. Dale, <a href="/A238605/b238605.txt">Table of n, a(n) for n = 1..1000</a> %t A238605 Select[Range[2000],PrimeOmega[#]==PrimeOmega[(#+1)/4]==2&] (* _Harvey P. Dale_, Oct 17 2021 *) %o A238605 (PARI) forstep( n=3,999,4,bigomega(n)==2 & bigomega((n+1)/4)==2 && print1(n",")) %Y A238605 Cf. A001414. %K A238605 nonn %O A238605 1,1 %A A238605 _M. F. Hasler_, Mar 01 2014