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A103775 Number of ways to write n! as product of distinct squarefree numbers. 3
1, 1, 2, 0, 1, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) = 0 for n > 7;

a(n) = A050326(A000142(n)).

LINKS

Table of n, a(n) for n=1..105.

Index entries for sequences related to factorial numbers.

FORMULA

a(n)=[C(2*n,n) mod 2]+{C[(n+1)^2,n+3] mod 2}+2*[C(n^2,n+2) mod 2]+{C[(n+10)^4,n+12] mod 2}+3*{C[(n+8)^4,n+10] mod 2} - Paolo P. Lava, Jan 07 2008

EXAMPLE

n=7, 7! = 1*2*3*4*5*6*7 = 5040 = 2*2*2*2*3*3*5*7: a(7) = #{2*3*6*10*14, 2*6*10*42, 2*6*14*30} = 3.

CROSSREFS

Cf. A103774.

Sequence in context: A163577 A132178 A039655 * A331594 A093057 A065334

Adjacent sequences:  A103772 A103773 A103774 * A103776 A103777 A103778

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Feb 15 2005

STATUS

approved

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Last modified February 18 03:40 EST 2020. Contains 332006 sequences. (Running on oeis4.)