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A053023
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Divisor function applied thrice to n!.
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1
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1, 2, 2, 3, 2, 4, 6, 6, 6, 5, 8, 8, 8, 8, 8, 9, 8, 10, 8, 10, 10, 12, 10, 10, 10, 15, 16, 16, 18, 16, 8, 16, 10, 12, 16, 18, 14, 3, 14, 16, 24, 16, 16, 20, 24, 24, 28, 24, 24, 16, 24, 24, 32, 32, 28, 32, 18, 20, 24, 28, 36, 32, 36, 24, 21, 24, 20, 40, 40, 30, 30, 36, 40, 42, 24, 32
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OFFSET
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1,2
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LINKS
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FORMULA
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EXAMPLE
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A036450(x) = 8 if x = 11!, 12!, 13!, 14!, 15!. The reversed sequences of these d-iterates are {2, 3, 4, 8, 24, 540, 39916800}, {2, 3, 4, 8, 24, 792, 479001600}, {2, 3, 4, 8, 30, 1584, 6227020800}, {2, 3, 4, 8, 30, 2592, 87178291200}, {2, 3, 4, 8, 42, 4032, 1307674368000}.
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MATHEMATICA
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a[n_] := Nest[DivisorSigma[0, #]&, n!, 3]; Array[a, 100] (* Amiram Eldar, Aug 12 2024 *)
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PROG
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(PARI) a(n) = numdiv(numdiv(numdiv(n!))); \\ Amiram Eldar, Aug 12 2024
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CROSSREFS
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KEYWORD
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nonn,changed
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AUTHOR
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STATUS
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approved
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