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A064937 Nonprimes k such that gcd(k, prime(k)^2 - 1) is 1. 1

%I

%S 1,25,49,55,77,119,133,143,155,161,169,185,187,203,209,217,221,235,

%T 247,275,287,289,295,301,325,329,361,365,371,377,391,403,407,415,425,

%U 427,437,451,455,469,473,485,493,497,505,511,517,527,529,539,553,559,583

%N Nonprimes k such that gcd(k, prime(k)^2 - 1) is 1.

%H Harry J. Smith, <a href="/A064937/b064937.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[ Range[600], !PrimeQ[ # ] && GCD[ #, Prime[ # ]^2 - 1] == 1 & ]

%o (PARI) { n=0; for (m=1, 10^9, if (isprime(m), next); if (gcd(m, prime(m)^2 - 1) == 1, write("b064937.txt", n++, " ", m); if (n==1000, return)) ) } \\ _Harry J. Smith_, Sep 30 2009

%Y Cf. A064830.

%K easy,nonn

%O 1,2

%A _Robert G. Wilson v_, Oct 26 2001

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Last modified June 22 19:28 EDT 2021. Contains 345388 sequences. (Running on oeis4.)