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A064394 Exponent of highest power of 2 dividing n! equals the largest prime < n. 3
4, 5, 8, 9, 22, 23, 26, 27, 32, 33, 50, 51, 56, 57, 70, 71, 76, 77, 82, 83, 94, 95, 100, 101, 112, 113, 118, 119, 128, 129, 134, 135, 176, 177, 186, 187, 196, 197, 266, 267, 274, 275, 280, 281, 296, 297, 342, 343, 352, 353, 358, 359, 364, 365, 372, 373, 386, 387 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

[n/2]+[n/4]+[n/8]+[n/16]+... = prevprime(n).

LINKS

Harvey P. Dale, Table of n, a(n) for n = 0..1000

EXAMPLE

8!=2^7*3^2*5*7, 23!=2^19*3^9*5^4*7^3*11^2*13*17*19*23.

MAPLE

for n from 3 to 10^3 do if sum(floor(n/(2^i)), i=1..15) = prevprime(n) then printf(`%d, `, n) fi; od:

MATHEMATICA

Select[Range[400], IntegerExponent[#!, 2]==NextPrime[#, -1]&] (* Harvey P. Dale, Sep 24 2013 *)

CROSSREFS

Cf. A011371, A007917.

Sequence in context: A228012 A067271 A268128 * A141220 A092022 A190200

Adjacent sequences:  A064391 A064392 A064393 * A064395 A064396 A064397

KEYWORD

nonn

AUTHOR

Vladeta Jovovic, Sep 29 2001

EXTENSIONS

More terms from James A. Sellers, Oct 01 2001

STATUS

approved

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Last modified October 21 22:47 EDT 2019. Contains 328315 sequences. (Running on oeis4.)