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
Keywords
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
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
Comments