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A160995 The smallest positive integer neither a divisor of n nor coprime to n. 2

%I

%S 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,

%T 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,

%U 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

%N The smallest positive integer neither a divisor of n nor coprime to n.

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

%H Charles R Greathouse IV, <a href="/A160995/b160995.txt">Table of n, a(n) for n = 2..10000</a>

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

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

%o (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

%K nonn

%O 2,1

%A _Leroy Quet_, Jun 01 2009

%E Extended by _Ray Chandler_, Jun 13 2009

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Last modified September 15 18:47 EDT 2019. Contains 327083 sequences. (Running on oeis4.)