A172017 Twin semiprimes (or twin biprimes): nonprimes of the form 6*k-+1 where 6*k-+1 are both semiprime (or both biprime).

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

1,1

Links

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

Mathematica

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

Crossrefs

Cf. A171697 (twin natural nonprimes).

Sequence in context: A234691 A252955 A171697 * A049048 A328973 A133626

Adjacent sequences: A172014 A172015 A172016 * A172018 A172019 A172020

Keyword

nonn

Author

Juri-Stepan Gerasimov, Jan 22 2010

Extensions

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

Status

approved