A105439 - OEIS

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A105439

a(n) = the smallest prime p such that p+2 and q+2 are prime; q is the n-th prime after p.

3, 5, 3, 5, 3, 17, 5, 3, 59, 5, 3, 11, 17, 5, 3, 29, 5, 3, 17, 41, 11, 41, 5, 3, 5, 3, 137, 11, 71, 5, 3, 5, 3, 17, 29, 11, 71, 5, 3, 5, 3, 5, 3, 11, 17, 5, 3, 137, 5, 3, 41, 11, 17, 5, 3, 41, 5, 3, 11, 227, 5, 3, 71, 11, 137, 5, 3, 41, 71, 41, 29, 59, 29, 17, 179, 11, 191, 5, 3, 5, 3

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OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

a(2)=5 because 5+2 and 11+2 are primes.

MATHEMATICA

pqr[n_]:=Module[{p=3}, While[AnyTrue[{p+2, NextPrime[p, n]+2}, CompositeQ], p= NextPrime[p]]; p]; Table[pqr[n], {n, 90}] (* Harvey P. Dale, Nov 12 2019 *)

CROSSREFS

Cf. A105443, A105444, A105445.

Sequence in context: A103506 A094929 A096634 * A142972 A020765 A112756

Adjacent sequences: A105436 A105437 A105438 * A105440 A105441 A105442

KEYWORD

nonn

AUTHOR

Cino Hilliard, May 02 2005

EXTENSIONS

Edited by Don Reble, Jun 11 2007

STATUS

approved