A264778 Numbers k such that 6*k+1, 3*k+2, 6*k+7 are all odd semiprimes.

113, 157, 193, 209, 211, 223, 231, 235, 251, 259, 307, 319, 345, 401, 415, 437, 463, 489, 521, 563, 567, 581, 599, 663, 673, 677, 701, 719, 731, 733, 771, 789, 811, 855, 857, 875, 883, 923, 935, 951, 961, 983, 993, 995, 997, 1017, 1023, 1031, 1047, 1089, 1097

Offset

1,1

Comments

Or odd numbers k such that the arithmetic progression 6*k+1, 6*k+4, 6*k+7 consists of twice a semiprime sandwiched between two semiprimes.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Mathematica

fQ[n_] := And[OddQ@ n, PrimeOmega@ n == 2]; Select[Range@ 1100,
AllTrue[{6 # + 1, 3 # + 2, 6 # + 7}, fQ] &] (* Michael De Vlieger, Nov 24 2015, Version 10 *)

Prog

(PARI) for(n=1, 1e4, if(n%2==1 && bigomega(6*n+1)==2 && bigomega(3*n+2)==2 && bigomega(6*n+7)==2, print1(n, ", "))); \\ Altug Alkan, Nov 24 2015

Crossrefs

Cf. A001358, A263510, A264779.

Sequence in context: A136078 A230255 A167631 * A142303 A152929 A142180

Adjacent sequences: A264775 A264776 A264777 * A264779 A264780 A264781

Keyword

nonn

Author

Vladimir Shevelev and Peter J. C. Moses, Nov 24 2015

Status

approved