A122984 Smallest positive composite number, relatively prime to n, such that a(n)+n is also composite.

8, 25, 22, 21, 4, 49, 8, 25, 16, 39, 4, 65, 8, 25, 34, 9, 4, 77, 6, 49, 4, 27, 4, 25, 8, 9, 8, 27, 4, 91, 4, 25, 16, 15, 4, 49, 8, 25, 10, 9, 4, 143, 6, 21, 4, 9, 4, 77, 6, 27, 4, 25, 4, 65, 8, 9, 8, 27, 4, 143, 4, 15, 22, 21, 4, 25, 8, 9, 8, 51, 4, 49, 4, 21, 16, 9, 4, 55, 6, 39, 4, 9, 4, 85

Offset: 1

Author

Franklin T. Adams-Watters, Sep 22 2006

Keywords

• easy
• nonn

Comments

Does not include every composite number; in particular, 12 is not present. If a(n) = 12, gcd(n,12) = 1, but then one of n+4 and n+8 is divisible by 3.

Crossrefs

Equals A122985(n) - n. Cf. A096076.