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A177464 The smallest positive k such that the n-th Mersenne prime +-k are two primes. 0
4, 12, 24, 30, 30, 66, 954, 1920, 30, 4116, 576, 214608 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

Smallest k>0 such that A000668(n)+k and A000668(n)-k are both prime.

LINKS

Table of n, a(n) for n=2..13.

FORMULA

a(n) = A082467(A000668(n)). - R. J. Mathar, Jan 23 2011

EXAMPLE

7+-4->primes, 31+-12->primes, 127+-24->primes, 8191+-30->primes, 131071+-30->primes, 524287+-66->primes..

MATHEMATICA

g[n_]:=2^Prime[n]-1; f[n_]:=Block[{k}, If[OddQ[n], k=2, k=1]; While[ !PrimeQ[n-k]||!PrimeQ[n+k], k+=2]; k]; lst={}; Do[If[PrimeQ[g[n]], AppendTo[lst, f[g[n]]]], {n, 2, 40}]; lst

CROSSREFS

Cf. A000668, A082467.

Sequence in context: A274187 A286040 A332608 * A316985 A273315 A301100

Adjacent sequences:  A177461 A177462 A177463 * A177465 A177466 A177467

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, May 09 2010

STATUS

approved

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Last modified October 21 05:28 EDT 2021. Contains 348141 sequences. (Running on oeis4.)