A101808 Number of primes between two consecutive even numbers.

1, 2, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0

Offset

0,2

Links

Table of n, a(n) for n=0..104.

Formula

a(n)=A101264(n), n>1. [From R. J. Mathar, Dec 13 2008]

Example

a(1)=2 because between 2 and 4 there are two primes: 2,3;
a(2)=1 because between 4 and 6 there is one prime: 5;
a(4)=0 because between 8 and 10 there are no primes.

Prog

(PARI) a(n) = if (n==0, 1, if (n==1, 2, isprime(2*n+1))) \\ Michel Marcus, Jun 03 2013

Crossrefs

Sequence in context: A157361 A369454 A224444 * A145865 A341281 A076452

Adjacent sequences: A101805 A101806 A101807 * A101809 A101810 A101811

Keyword

easy,nonn

Author

Giovanni Teofilatto, Jan 27 2005

Status

approved