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A142247 Primes of the four types: {2^Prime[n] - 1, 2^Prime[n] + 1, 2^Prime[n] - 3, 2^Prime[n] + 3}. 0
3, 5, 7, 11, 29, 31, 127, 131, 8191, 131071, 524287, 536870909, 2147483647, 2305843009213693951, 147573952589676412931, 618970019642690137449562111, 162259276829213363391578010288127 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..17.

FORMULA

a(n) = If[PrimeQ[{2^Prime[n] - 1, 2^Prime[n] + 1, 2^Prime[n] - 3, 2^Prime[n] + 3}, which of them is prime]

MATHEMATICA

f[n_] := If[PrimeQ[2^Prime[n] - 1] || PrimeQ[2^Prime[n] + 1] || PrimeQ[2^Prime[n] - 3] || PrimeQ[2^Prime[n] + 3], {2^Prime[n] - 1, 2^Prime[n] + 1, 2^Prime[n] - 3, 2^Prime[n] + 3}, {}]; a = Flatten[Table[f[n], {n, 1, 100}]]; Union[Flatten[Table[If[PrimeQ[a[[n]]], a[[n]], {}], {n, 1, Length[a]}]]]

CROSSREFS

Sequence in context: A265687 A023368 A295973 * A167895 A106712 A019391

Adjacent sequences:  A142244 A142245 A142246 * A142248 A142249 A142250

KEYWORD

nonn,uned

AUTHOR

Roger L. Bagula, Sep 18 2008

STATUS

approved

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Last modified April 19 19:09 EDT 2019. Contains 322290 sequences. (Running on oeis4.)