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A129906
n!/(n^2) when an integer.
2
1, 20, 630, 4480, 36288, 3326400, 444787200, 5811886080, 81729648000, 19760412672000, 6082255020441600, 115852476579840000, 2322315553259520000, 1077167364120207360000, 24817936069329577574400, 596585001666576384000000, 14936720782466875392000000
OFFSET
1,2
COMMENTS
Also see comments in A046022 = primes together with 1 and 4.
LINKS
FORMULA
a(n) = A000142(m)/A000290(m) where m = A056653(n). - Jason Yuen, Sep 20 2024
MATHEMATICA
f[n_]:=If[PrimeQ[n]||n == 4, 0, n!/n^2]; Select[Table[f[n], {n, 1, 40}], #>0&] (* Geoffrey Critzer, Oct 26 2012 *)
Select[#!/#^2&/@Range[30], IntegerQ] (* Harvey P. Dale, Jul 17 2024 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Jun 09 2007
EXTENSIONS
More terms from Alois P. Heinz, Oct 26 2012
STATUS
approved