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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also see comments in A046022 = primes together with 1 and 4.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..150

FORMULA

{n!/(n^2) when an integer} = {n!/(n^2) where n is a nonnegative integer other than 4 or a prime} = {A000142(n)/A000290(n) when an integer.

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 *)

CROSSREFS

Cf. A000142, A000290, A046022.

Sequence in context: A015268 A202577 A059420 * A125722 A226731 A201724

Adjacent sequences:  A129903 A129904 A129905 * A129907 A129908 A129909

KEYWORD

easy,nonn

AUTHOR

Jonathan Vos Post, Jun 09 2007

EXTENSIONS

More terms from Alois P. Heinz, Oct 26 2012

STATUS

approved

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Last modified April 24 00:02 EDT 2019. Contains 322404 sequences. (Running on oeis4.)