A177460 Smallest k such that A000217(n)+k and A000217(n)-k are both prime.

0, 1, 3, 2, 2, 9, 5, 2, 12, 5, 5, 12, 2, 7, 27, 4, 8, 9, 13, 2, 24, 5, 7, 12, 2, 5, 27, 4, 2, 75, 19, 38, 18, 11, 7, 30, 2, 7, 9, 2, 16, 63, 7, 4, 12, 25, 5, 12, 16, 35, 51, 2, 2, 9, 13, 16, 12, 17, 41, 60, 20, 13, 51, 8, 32, 9, 5, 22, 18, 35, 19, 12, 22, 7, 75, 34, 2, 93, 11, 2, 30, 25, 11

Offset

2,3

Links

Table of n, a(n) for n=2..84.

Example

3+-0->primes. 6+-1->primes. 10+-3->primes. 15+-2->primes,..

Mathematica

f[n_]:=Block[{k}, If[OddQ[n], k=0, k=1]; While[ !PrimeQ[n-k]||!PrimeQ[n+k], k+=2]; k]; Table[f[n*(n+1)/2], {n, 2, 5!}]

Crossrefs

Cf. A000217, A172989, A172990.

Sequence in context: A195422 A176530 A011319 * A091015 A256097 A058147

Adjacent sequences: A177457 A177458 A177459 * A177461 A177462 A177463

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, May 09 2010

Extensions

Definition rephrased and offset adapted by R. J. Mathar, Aug 15 2010

Status

approved