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A122984 Smallest positive composite number, relatively prime to n, such that a(n)+n is also composite. 2
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 (list; graph; refs; listen; history; text; internal format)
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: A103954 A217012 A200838 * A254341 A188477 A045860

Adjacent sequences:  A122981 A122982 A122983 * A122985 A122986 A122987

KEYWORD

easy,nonn

AUTHOR

Franklin T. Adams-Watters, Sep 22 2006

STATUS

approved

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Last modified November 19 03:59 EST 2017. Contains 294912 sequences.