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A173086 Numbers n such that n, n^2 - 6, and n^2 + 6 are semiprime. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A197664 A099606 A149231 * A081565 A151611 A208236

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

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Last modified September 18 18:38 EDT 2019. Contains 327180 sequences. (Running on oeis4.)