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A160995 The smallest positive integer neither a divisor of n nor coprime to n. 2
4, 6, 6, 10, 4, 14, 6, 6, 4, 22, 8, 26, 4, 6, 6, 34, 4, 38, 6, 6, 4, 46, 9, 10, 4, 6, 6, 58, 4, 62, 6, 6, 4, 10, 8, 74, 4, 6, 6, 82, 4, 86, 6, 6, 4, 94, 9, 14, 4, 6, 6, 106, 4, 10, 6, 6, 4, 118, 8, 122, 4, 6, 6, 10, 4, 134, 6, 6, 4, 142, 10, 146, 4, 6, 6, 14, 4, 158, 6, 6, 4, 166, 8, 10, 4, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

a(1) doesn't exist because 1 is coprime to all integers.

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 2..10000

FORMULA

a(p) = 2p, for all primes p.

PROG

(PARI) a(n)=for(k=4, 2*n, if(gcd(n, k)>1 && n%k, return(k))) \\ Charles R Greathouse IV, Apr 05 2013

(PARI) a(n)=my(f=factor(n), b); forprime(p=2, , if(n%p, b=p*f[1, 1]; break)); for(i=1, #f[, 1], b=min(b, f[i, 1]^(f[i, 2]+1))); b \\ Charles R Greathouse IV, Apr 05 2013

CROSSREFS

Sequence in context: A199172 A323674 A183986 * A215454 A155750 A159475

Adjacent sequences:  A160992 A160993 A160994 * A160996 A160997 A160998

KEYWORD

nonn

AUTHOR

Leroy Quet, Jun 01 2009

EXTENSIONS

Extended by Ray Chandler, Jun 13 2009

STATUS

approved

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Last modified August 23 22:20 EDT 2019. Contains 326254 sequences. (Running on oeis4.)