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 A364028 #7 Jul 01 2023 16:55:11 %S A364028 65,77,115,141,159,295,301,303,319,329,403,427,473,481,515,533,581, %T A364028 589,629,655,671,679,703,713,717,785,835,869,871,943,965,1041,1059, %U A364028 1099,1111,1139,1145,1195,1199,1207,1241,1337,1339,1349,1363,1387,1461,1469,1501,1507,1529 %N A364028 Odd squarefree semiprimes s = p*q such that p + q and p - q are not squarefree. %e A364028 a(1) = 65 = 13*5; 13+5 = 2*3^2, 13-5 = 2^3; %e A364028 a(2) = 77 = 11*7; 11+7 = 2*3^2, 11-7 = 2^2; %e A364028 a(3) = 115 = 23*5; 23+5 = 2^2*7, 23-5 = 2*3^2. %o A364028 (PARI) forstep (k = 15, 1529, 2, if (omega(k)==2 && bigomega(k)==2, my (F=factorint(k)); if ( !issquarefree(F[2,1]-F[1,1]) && !issquarefree(F[2,1]+F[1,1]), print1(k,", ")))) %Y A364028 Cf. A046388, A198512, A090967. %K A364028 nonn %O A364028 1,1 %A A364028 _Hugo Pfoertner_, Jul 01 2023