A108258 Consider primes p and q such that p = 3^k + 20 and q = 3^(k+1) + 20 for some k; sequence gives values of q.

29, 47, 101, 263, 6581, 177167

Offset

1,1

Links

Table of n, a(n) for n=1..6.

Example

3^1 + 20 = 23, 3^2 + 20 = 29.

Mathematica

Transpose[Select[Partition[#+20&/@(3^Range[50]), 2, 1], AllTrue[ #, PrimeQ]&]] [[2]] (* The program uses the function AllTrue from Mathematica version 10 *) (* Harvey P. Dale, Oct 29 2014 *)

Prog

(PARI) g(m, n, b) = { for(x=0, n, y=m+b^x+b%2; z=m+b^(x+1)+b%2; if(isprime(y)&isprime(z), print1(z", ") ) ) }

Crossrefs

Cf. A108249.

Sequence in context: A106754 A222413 A063642 * A232236 A228585 A042947

Adjacent sequences: A108255 A108256 A108257 * A108259 A108260 A108261

Keyword

nonn

Author

Cino Hilliard, Jun 29 2005

Status

approved