A127955 Composite numbers of the form (2^p+1)/3 where p is a prime.

178956971, 45812984491, 733007751851, 46912496118443, 3002399751580331, 192153584101141163, 49191317529892137643, 787061080478274202283, 3148244321913096809131, 3223802185639011132549803

Offset: 1

Author

Artur Jasinski, Feb 09 2007

Keywords

• nonn

Comments

If p-1 is squarefree, the terms are overpseudoprimes (see A141232). - Vladimir Shevelev, Jul 15 2008

Links

• G. C. Greubel, Table of n, a(n) for n = 1..440

Crossrefs

Cf. A000979, A000978, A124400, A126614, A127956, A127957.

Programs

Mathematica

a = {}; Do[c = (2^Prime[x] + 1)/3; If[PrimeQ[c] == False, AppendTo[a, c]], {x, 2, 30}]; a
Select[(2^Prime[Range[2,30]]+1)/3,CompositeQ] (* Harvey P. Dale, Feb 04 2015 *)