A173086 Numbers n such that n, n^2 - 6, and n^2 + 6 are semiprime.

4, 10, 49, 95, 121, 217, 247, 289, 295, 301, 305, 335, 371, 427, 469, 493, 535, 551, 581, 583, 707, 721, 745, 749, 767, 815, 817, 835, 851, 893, 899, 901, 973, 1099, 1169, 1205, 1219, 1253, 1333, 1349, 1379, 1405, 1501, 1603, 1685, 1711, 1739, 1751, 1757, 1765

Offset

1,1

Links

Table of n, a(n) for n=1..50.

Example

4=2*2, 4^2-6=10=2*5, 4^2+6=22=2*11, so 4 is in the sequence.

Mathematica

f[n_]:=Last/@FactorInteger[n]=={1, 1}||Last/@FactorInteger[n]=={2}; lst={}; Do[If[f[n], a=n^2-6; b=n^2+6; If[f[a]&&f[b], AppendTo[lst, n]]], {n, 8!}]; lst

Crossrefs

Cf. A001358, A173082, A173083, A173084, A173085

Sequence in context: A149231 A335873 A364281 * A081565 A151611 A351046

Adjacent sequences: A173083 A173084 A173085 * A173087 A173088 A173089

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Feb 09 2010

Extensions

Edited by Charles R Greathouse IV, Apr 06 2010

Status

approved