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

1,1

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.

Links

Table of n, a(n) for n=1..84.

Crossrefs

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

Sequence in context: A217012 A200838 A302160 * A254341 A188477 A302632

Adjacent sequences: A122981 A122982 A122983 * A122985 A122986 A122987

Keyword

easy,nonn

Author

Franklin T. Adams-Watters, Sep 22 2006

Status

approved