

A222638


Product, for k <= n, of the squarefree parts of the total number of arrangements of a set with k elements.


1



1, 2, 10, 10, 650, 211900, 414688300, 56812297100, 6226684574457100, 6142063931090228011000, 60585938964731049213533111000, 1643471023248326636197980531190858000, 12662130715971848810220521992462621415290000, 214329322370515670487612822767624011121300533960940000
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OFFSET

0,2


COMMENTS

In their abstract, Luca and Shparlinski write: "In this note, we show that if we write floor(e*n!) = s(n)*u(n)^2, where s(n) is squarefree then S(N) = prod(n<=N) has at least C log log N distinct prime factors for some absolute constant C > 0 and sufficiently large N. A similar result is obtained for the total number of distinct primes dividing the mth powerfree part of s(n) as n ranges from 1 to N, where m = 3 is a positive integer. As an application of such results, we give an upper bound on the number of n <= N such that floor(e*n!) is a square."


LINKS

Table of n, a(n) for n=0..13.
F. Luca and I. E. Shparlinski, On the squarefree parts of [ e n! ], Glasgow Math. J., 49 (2007), 391403.


FORMULA

a(n) = Prod_{k <= n} A222637(k) = Prod_{k <= n} core(A000522(k)).


PROG

(PARI) a(n) = prod(i=1, n, core(i! * polcoeff(exp(x + x*O(x^i)) / (1  x), i)))


CROSSREFS

Sequence in context: A232500 A033466 A193181 * A299982 A089601 A171893
Adjacent sequences: A222635 A222636 A222637 * A222639 A222640 A222641


KEYWORD

nonn


AUTHOR

Michel Marcus, Feb 27 2013


STATUS

approved



