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A179215
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Product of squarefree numbers less than n+1.
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9
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1, 1, 2, 6, 6, 30, 180, 1260, 1260, 1260, 12600, 138600, 138600, 1801800, 25225200, 378378000, 378378000, 6432426000, 6432426000, 122216094000, 122216094000, 2566537974000, 56463835428000, 1298668214844000, 1298668214844000, 1298668214844000, 33765373585944000
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history;
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OFFSET
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0,3
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LINKS
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G. C. Greubel, Table of n, a(n) for n = 0..680
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FORMULA
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a(n) = Product_{k=1..n} k^A008966(k).
A001221(a(n)) = A000720(n).
Subsequence of A025487.
A034386(n) <= a(n) <= A000142(n).
A179214(n) = a(2*n)/a(n-1) for n>0.
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MAPLE
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a:= proc(n) option remember; `if`(n=0, 1,
a(n-1)*`if`(issqrfree(n), n, 1))
end:
seq(a(n), n=0..27); # Alois P. Heinz, Sep 20 2021
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MATHEMATICA
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With[{sfnos=Select[Range[50], SquareFreeQ]}, Table[Times@@Select[sfnos, #<n+1&], {n, 0, 30}]] (* Harvey P. Dale, Jun 13 2011 *)
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PROG
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(PARI) a(n) = prod(k=1, n, if (issquarefree(k), k, 1)); \\ Michel Marcus, Sep 20 2021
(PARI) a(n) = my(p=1); forsquarefree(x=1, n, p*=x[1]); p; \\ Michel Marcus, Sep 20 2021
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CROSSREFS
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Cf. A013928, A066779, A005117, A008966, A179214.
Cf. A000142, A000720, A001221, A025487, A034386.
Sequence in context: A113461 A061558 A123144 * A069260 A056603 A019198
Adjacent sequences: A179212 A179213 A179214 * A179216 A179217 A179218
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller, Jul 05 2010
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EXTENSIONS
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Definition corrected by Harvey P. Dale, Jun 13 2011
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STATUS
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approved
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