A087298 Exponent of 2 in factorization of (3n)!.

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

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: A115566 A364840 A190507 * A237707 A211642 A127958

Adjacent sequences: A087295 A087296 A087297 * A087299 A087300 A087301

Keyword

nonn,easy

Author

Ralf Stephan, Oct 20 2003

Status

approved