A364028 Odd squarefree semiprimes s = p*q such that p + q and p - q are not squarefree.

65, 77, 115, 141, 159, 295, 301, 303, 319, 329, 403, 427, 473, 481, 515, 533, 581, 589, 629, 655, 671, 679, 703, 713, 717, 785, 835, 869, 871, 943, 965, 1041, 1059, 1099, 1111, 1139, 1145, 1195, 1199, 1207, 1241, 1337, 1339, 1349, 1363, 1387, 1461, 1469, 1501, 1507, 1529

Offset

1,1

Links

Table of n, a(n) for n=1..51.

Example

a(1) = 65 = 13*5; 13+5 = 2*3^2, 13-5 = 2^3;
a(2) = 77 = 11*7; 11+7 = 2*3^2, 11-7 = 2^2;
a(3) = 115 = 23*5; 23+5 = 2^2*7, 23-5 = 2*3^2.

Prog

(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, ", "))))

Crossrefs

Cf. A046388, A198512, A090967.

Sequence in context: A282113 A060877 A113688 * A369662 A369664 A214484

Adjacent sequences: A364025 A364026 A364027 * A364029 A364030 A364031

Keyword

nonn

Author

Hugo Pfoertner, Jul 01 2023

Status

approved