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%I #17 Sep 21 2024 02:25:37
%S 1,20,630,4480,36288,3326400,444787200,5811886080,81729648000,
%T 19760412672000,6082255020441600,115852476579840000,
%U 2322315553259520000,1077167364120207360000,24817936069329577574400,596585001666576384000000,14936720782466875392000000
%N n!/(n^2) when an integer.
%C Also see comments in A046022 = primes together with 1 and 4.
%H Alois P. Heinz, <a href="/A129906/b129906.txt">Table of n, a(n) for n = 1..150</a>
%F a(n) = A000142(m)/A000290(m) where m = A056653(n). - _Jason Yuen_, Sep 20 2024
%t f[n_]:=If[PrimeQ[n]||n == 4,0,n!/n^2];Select[Table[f[n],{n,1,40}],#>0&] (* _Geoffrey Critzer_, Oct 26 2012 *)
%t Select[#!/#^2&/@Range[30],IntegerQ] (* _Harvey P. Dale_, Jul 17 2024 *)
%Y Cf. A000142, A000290, A046022, A056653.
%K easy,nonn
%O 1,2
%A _Jonathan Vos Post_, Jun 09 2007
%E More terms from _Alois P. Heinz_, Oct 26 2012