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A066788 a(n) = gcd(phi(n), n^2 + 1). 1

%I

%S 1,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,5,2,1,2,1,2,1,2,1,2,1,10,1,

%T 2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,5,2,1,2,1,2,1,

%U 2,1,2,1,2,1,2,1,10,1,2,1,2,5,2,1,2,1,2,5,2,1,2,1,10,1,2,1,2,1,2,1,2,1,2

%N a(n) = gcd(phi(n), n^2 + 1).

%H Harry J. Smith, <a href="/A066788/b066788.txt">Table of n, a(n) for n = 1..1000</a>

%t Table[GCD[EulerPhi[n],n^2+1],{n,110}] (* _Harvey P. Dale_, Feb 14 2018 *)

%o (PARI) { for (n=1, 1000, write("b066788.txt", n, " ", gcd( eulerphi(n), n^2 + 1)) ) } \\ _Harry J. Smith_, Mar 26 2010

%K nonn

%O 1,3

%A _Benoit Cloitre_, Jan 18 2002

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Last modified January 23 20:47 EST 2022. Contains 350515 sequences. (Running on oeis4.)