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A087298 Exponent of 2 in factorization of (3n)!. 0
1, 4, 7, 10, 11, 16, 18, 22, 23, 26, 31, 34, 35, 39, 41, 46, 47, 50, 53, 56, 57, 64, 66, 70, 71, 74, 78, 81, 82, 86, 88, 94, 95, 98, 101, 104, 105, 110, 112, 116, 117, 120, 127, 130, 131, 135, 137, 142, 143, 146, 149, 152, 153, 159, 161, 165, 166 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(2n) = a(n) + 3n.

LINKS

Table of n, a(n) for n=1..57.

FORMULA

Sum[k=1..inf, floor(3n/2^k)].

EXAMPLE

(3*5)! = 2^11 * 638512875, so a(5) = 11.

PROG

(PARI) a(n)=valuation((3*n)!, 2)

CROSSREFS

Cf. A011371 (n!), A005187 ((2n)!).

Sequence in context: A082206 A115566 A190507 * A237707 A211642 A127958

Adjacent sequences:  A087295 A087296 A087297 * A087299 A087300 A087301

KEYWORD

nonn,easy

AUTHOR

Ralf Stephan, Oct 20 2003

STATUS

approved

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Last modified August 11 06:25 EDT 2020. Contains 336422 sequences. (Running on oeis4.)