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a(n) = A002034(n)!/n.
(Formerly M1669)
5

%I M1669 #21 May 09 2017 10:41:24

%S 1,1,2,6,24,1,720,3,80,12,3628800,2,479001600,360,8,45,20922789888000,

%T 40,6402373705728000,6,240,1814400,1124000727777607680000,1,145152,

%U 239500800,13440,180,304888344611713860501504000000

%N a(n) = A002034(n)!/n.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H A. J. Kempner, <a href="http://www.jstor.org/stable/2972639">Miscellanea</a>, Amer. Math. Monthly, 25 (1918), 201-210 [ See Section II, "Concerning the smallest integer m! divisible by a given integer n". ]

%t a[n_] := Module[{m = 1, x = n, as = 1, p}, While[x > 1, m++; p = GCD[x, m]; x = x/p; as *= m/p]; as]; Array[a, 30] (* _Jean-François Alcover_, May 09 2017, after _Antonio Roldán_ *)

%o (PARI) a(n)={local(m=1,x=n,as=1,p);while(x>1,m++;p=gcd(x,m);x=x/p;as*=m/p);as} \\ _Antonio Roldán_, Apr 04 2015

%K nonn,nice

%O 1,3

%A _N. J. A. Sloane_, _Robert G. Wilson v_