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A179215 Product of squarefree numbers less than n+1. 9
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..680

FORMULA

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.

MAPLE

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

MATHEMATICA

With[{sfnos=Select[Range[50], SquareFreeQ]}, Table[Times@@Select[sfnos, #<n+1&], {n, 0, 30}]] (* Harvey P. Dale, Jun 13 2011 *)

PROG

(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

CROSSREFS

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

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jul 05 2010

EXTENSIONS

Definition corrected by Harvey P. Dale, Jun 13 2011

STATUS

approved

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Last modified May 28 15:04 EDT 2022. Contains 354115 sequences. (Running on oeis4.)