A071127 Number of times there is a prime p < n such that 2n+p is prime.

0, 0, 0, 1, 1, 1, 2, 2, 1, 1, 1, 2, 3, 2, 3, 2, 3, 4, 2, 4, 4, 2, 2, 5, 4, 2, 5, 5, 2, 6, 3, 3, 6, 4, 4, 5, 3, 5, 6, 4, 3, 6, 5, 3, 8, 3, 6, 8, 5, 5, 6, 4, 4, 7, 6, 2, 6, 4, 3, 11, 5, 4, 9, 5, 5, 9, 7, 6, 9, 6, 3, 10, 6, 4, 11, 7, 6, 10, 5, 9, 11, 5, 6, 12, 8, 5, 10, 6, 6, 13, 7, 6, 11, 8, 8, 11, 7, 8, 11

Offset

1,7

Links

T. D. Noe, Table of n, a(n) for n=1..10000

Example

a(7)=2 because 14+3 and 14+5 are primes.

Mathematica

For[lst={}; n=1, n<=100, n++, cnt=0; k=1; While[Prime[k]<n, If[PrimeQ[2n+Prime[k]], cnt++ ]; k++ ]; AppendTo[lst, cnt]]; lst

Crossrefs

Cf. A071137.

Sequence in context: A201159 A356225 A047070 * A029381 A343558 A297877

Adjacent sequences: A071124 A071125 A071126 * A071128 A071129 A071130

Keyword

easy,nonn

Author

T. D. Noe, May 28 2002

Status

approved