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a(n) = product of the positive integers k, k<= n, such that the positive integers <= k and coprime to k are also coprime to n.
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%I #9 Sep 27 2019 12:39:49

%S 1,2,6,8,120,12,5040,384,324,80,39916800,144,6227020800,672,90,

%T 10321920,355687428096000,2592,121645100408832000,1600,756,84480,

%U 25852016738884976640000,62208,9000000,1198080,14285134080,18816

%N a(n) = product of the positive integers k, k<= n, such that the positive integers <= k and coprime to k are also coprime to n.

%e The positive integers k, k <= 6, where the positive integers <= k and coprime to k are also coprime to 6, are 1,2,6. So a(6) = 1*2*6 = 12.

%t f[n_] := Select[Range[n], GCD[ #, n] == 1 &];g[n_] := Select[Range[n], Times @@ GCD[f[ # ], n] == 1 &];Times @@@ Table[g[n], {n, 30}] (* Ray Chandler, Dec 24 2006 *)

%Y Cf. A126260, A124611.

%K nonn

%O 1,2

%A _Leroy Quet_, Dec 24 2006

%E Extended by _Ray Chandler_, Dec 24 2006