A126072 a(n) = least j>n such that one of p(n)#+p(j)#-1 and p(n)#+p(j)#+1 is prime, or 0 if no such prime exists.

2, 3, 4, 5, 6, 7, 9, 9, 15, 11, 13, 13, 18, 20, 29, 19, 23, 21, 21, 21, 23, 32, 27, 42, 28, 30, 30, 34, 37, 77, 33, 74, 59, 45, 53, 45, 38, 46, 43, 47, 55, 44, 47, 54, 76, 48, 49, 50, 69, 56, 60, 0, 66, 68, 94, 57, 69, 84, 86, 73, 65, 73, 71, 114, 70, 91, 98, 80, 72, 84, 79, 76

Offset

1,1

Comments

The first 0 is for n=52. Are there others?

Links

Table of n, a(n) for n=1..72.

Example

2+2*3-1 = 7 so a(1) = 2.
2*3+2*3*5-1 = 35 is composite but 2*3+2*3*5+1 = 37 is prime so a(2) = 3.

Crossrefs

Sequence in context: A071191 A300903 A097428 * A265570 A265554 A082463

Adjacent sequences: A126069 A126070 A126071 * A126073 A126074 A126075

Keyword

nonn

Author

Pierre CAMI, Mar 01 2007

Status

approved