A092953 Number of primes of the form n+p, where p is a prime < n.

0, 0, 1, 1, 1, 1, 0, 2, 1, 2, 1, 3, 0, 2, 1, 3, 1, 3, 0, 3, 1, 2, 0, 6, 0, 4, 1, 3, 1, 6, 0, 3, 0, 4, 1, 6, 0, 4, 1, 5, 1, 8, 0, 4, 1, 4, 0, 7, 0, 6, 1, 4, 0, 9, 0, 8, 1, 4, 1, 11, 0, 5, 0, 5, 1, 11, 0, 6, 1, 8, 1, 9, 0, 4, 0, 7, 1, 11, 0, 7, 1, 4, 0, 13, 0, 7, 1, 5, 0, 15, 0, 7, 0, 8, 1, 13, 0, 8, 1, 9, 1, 11

Offset: 1

Author

Amarnath Murthy, Mar 24 2004

Keywords

• nonn

Comments

Might be called the additive primability of n.

a(A007921(n))=0; for n > 2: a(A030173(n)) > 0 and a(A040976(n)) = 1. - Reinhard Zumkeller, Nov 10 2012

Examples

			a(26) = 4: the primes are 29, 31, 37 and 43.
		

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A092954.

Cf. A061357.

Programs

Haskell

a092953 n = sum $
   zipWith (\u v -> a010051' u * a010051' v) [1 .. n - 1] [n + 1 ..]
-- Reinhard Zumkeller, Nov 10 2012

PARI

for(n=1,105,c=0;forprime(p=2,n-1,if(isprime(n+p),c++));print1(c,","))

Extensions

More terms from Klaus Brockhaus and Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 25 2004