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A090618 Highest power of 9 dividing n!. 3
0, 0, 0, 0, 0, 0, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 7, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 9, 9, 9, 10, 10, 10, 11, 11, 11, 11, 11, 11, 13, 13, 13, 13, 13, 13, 14, 14, 14, 15, 15, 15, 15, 15, 15, 16, 16, 16, 17, 17, 17, 17, 17, 17, 18, 18, 18, 20, 20, 20, 20 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,10

LINKS

Table of n, a(n) for n=0..84.

FORMULA

a(n) =A090622(n, 9) =[A054861(n)/2] =[([n/3]+[n/9]+[n/27]+[n/81]+...)/2].

EXAMPLE

a(9)=2 since 9!=362880=9^2*4480.

MATHEMATICA

IntegerExponent[Range[0, 90]!, 9] (* Harvey P. Dale, Jun 07 2016 *)

CROSSREFS

Cf. A011371, A054861, A090616, A027868, A054896, A090617.

Sequence in context: A280952 A235122 A131996 * A186444 A072748 A174631

Adjacent sequences:  A090615 A090616 A090617 * A090619 A090620 A090621

KEYWORD

nonn

AUTHOR

Henry Bottomley, Dec 06 2003

STATUS

approved

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Last modified August 12 17:17 EDT 2020. Contains 336439 sequences. (Running on oeis4.)