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A127955 Composite numbers of the form (2^p+1)/3 where p is a prime. 13
178956971, 45812984491, 733007751851, 46912496118443, 3002399751580331, 192153584101141163, 49191317529892137643, 787061080478274202283, 3148244321913096809131, 3223802185639011132549803 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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

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 *)

CROSSREFS

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

Sequence in context: A300555 A213966 A206520 * A047738 A079323 A228760

Adjacent sequences:  A127952 A127953 A127954 * A127956 A127957 A127958

KEYWORD

nonn

AUTHOR

Artur Jasinski, Feb 09 2007

STATUS

approved

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Last modified August 21 12:11 EDT 2018. Contains 313940 sequences. (Running on oeis4.)