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A370201
a(n) = denominator((n!)^2/(2*(n-2)!*n^n)).
1
2, 3, 16, 125, 108, 16807, 32768, 531441, 312500, 2357947691, 5971968, 1792160394037, 15818613944, 320361328125, 70368744177664, 2862423051509815793, 10167463313316, 5480386857784802185939, 64000000000000000, 41209797661291758429, 489272723587316370328
OFFSET
2,1
COMMENTS
a(n) is the denominator of the probability that a sequence of n integers randomly chosen from [n] contains exactly n - 1 different integers (see Brualdi, pp. 57-58).
REFERENCES
Richard A. Brualdi, Introductory Combinatorics, 5th ed. Pearson Education Inc., 2009.
MATHEMATICA
a[n_]:=Denominator[n!^2/(2(n-2)!n^n)]; Array[a, 21, 2]
CROSSREFS
Cf. A000142, A000312, A001044, A370200 (numerators).
Sequence in context: A375684 A067848 A269067 * A356882 A139802 A292207
KEYWORD
nonn,frac
AUTHOR
Stefano Spezia, Feb 11 2024
STATUS
approved