A076473 Number of pairs (p,q) of successive primes with p+q<=n and gcd(p+q,n)=1.

0, 0, 0, 0, 0, 1, 1, 1, 2, 0, 2, 1, 3, 1, 1, 1, 3, 1, 4, 0, 2, 1, 4, 1, 4, 1, 2, 1, 5, 0, 6, 1, 2, 1, 4, 1, 7, 1, 2, 0, 7, 1, 8, 1, 1, 1, 8, 1, 7, 0, 2, 1, 9, 1, 7, 1, 3, 1, 9, 0, 10, 1, 3, 1, 6, 1, 10, 1, 4, 0, 11, 1, 11, 1, 3, 1, 10, 1, 12, 0, 4, 1, 12, 1, 9, 1, 4, 1, 13, 0, 10, 1, 4, 1, 10, 1, 14, 1, 4

Offset

1,9

Comments

a(n) = A076471(n) - A076472(n).

Links

Table of n, a(n) for n=1..99.

Example

n=27: gcd(2+3,27)=1, gcd(3+5,27)=1, gcd(5+7,27)=3, gcd(7+11,27)=9, gcd(11+13,27)=3, hence a(27)=2.

Crossrefs

Cf. A000010.

Sequence in context: A191247 A308263 A028932 * A163160 A306696 A237184

Adjacent sequences: A076470 A076471 A076472 * A076474 A076475 A076476

Keyword

nonn

Author

Reinhard Zumkeller, Oct 14 2002

Status

approved