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With the exception of n=4, if n is composite, a(n) = 0. If n is prime, a(n) = n*(n-1). For example, a(11) = 11*10 = 110, a(41) = 41*40 = 1640. - Gary Detlefs, May 01 2010
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a(n) = A174530(n)*(A174530(n)-1) for n>=5. - Filip Zaludek, Oct 13 2016
a(n) = A174530(n)*(A174530(n)-1) for n>=5. - Filip Zaludek, Oct 13 2016
_Roman Stawski (roman.stawski(AT)wanadoo.fr), _, Jul 05 2002
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Table[Mod[n!, n^2], {n, 79}] (* or *)
Table[Which[n == 4, Mod[n!, n^2], PrimeQ@ n, n (n - 1), True, 0], {n, 79}] (* Michael De Vlieger, Oct 14 2016 *)
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