A172017 Twin semiprimes: nonprimes of the form 6*k-+1 where 6*k-+1 are both semiprime.

119, 121, 143, 145, 185, 187, 203, 205, 215, 217, 287, 289, 299, 301, 413, 415, 515, 517, 527, 529, 533, 535, 551, 553, 581, 583, 695, 697, 779, 781, 791, 793, 815, 817, 869, 871, 893, 895, 899, 901, 959, 961, 1055, 1057, 1079, 1081, 1133, 1135, 1139

Offset: 1

Author

Juri-Stepan Gerasimov, Jan 22 2010

Keywords

• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..2000

Crossrefs

Cf. A001358 (semiprimes), A171697 (twin natural nonprimes).

Programs

Mathematica

Select[{#-1,#+1}&/@(6*Range[200]),PrimeOmega[#]=={2,2}&]//Flatten (* Harvey P. Dale, Nov 14 2018 *)

Extensions

Corrected (623,625 removed) by R. J. Mathar, May 22 2010