A175710 Numbers k such that k-4, k and k+4 are all semiprimes.

10, 91, 115, 119, 205, 209, 213, 217, 291, 295, 299, 305, 323, 407, 411, 485, 489, 493, 497, 501, 515, 533, 685, 699, 703, 717, 749, 767, 785, 789, 803, 917, 955, 989, 1007, 1077, 1115, 1137, 1141, 1145, 1195, 1199, 1203, 1207, 1257, 1267, 1333, 1343, 1347

Offset: 1

Author

Juri-Stepan Gerasimov, Aug 12 2010

Keywords

• nonn

Comments

If k is a term, one of k-4, k and k+4 is 3 times a prime. - Robert Israel, Mar 25 2025

Examples

			a(1)=10 because 10-4=6, 10 and 10+4=14 are all semiprimes.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001358, A175612, A175648, A175664.

Programs

Maple

SP:= select(t -> numtheory:-bigomega(t) = 2, {$1..10000}):
sort(convert(SP intersect (SP +~ 4) intersect (SP -~ 4),list)); # Robert Israel, Mar 25 2025

Extensions

Corrected (299, 411 etc inserted) by R. J. Mathar, Aug 13 2010

Name edited by Robert Israel, Mar 25 2025