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A064393
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Exponent of highest power of 2 dividing n! equals the largest prime <= n.
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1
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4, 8, 9, 22, 26, 27, 32, 33, 50, 51, 56, 57, 70, 76, 77, 82, 94, 95, 100, 112, 118, 119, 128, 129, 134, 135, 176, 177, 186, 187, 196, 266, 267, 274, 275, 280, 296, 297, 342, 343, 352, 358, 364, 365, 372, 386, 387, 392, 393, 400, 406, 407, 426, 427, 454, 455
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| [n/2]+[n/4]+[n/8]+[n/16]+... = prevprime(n+1).
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EXAMPLE
| 4!=2^3*3, 8!=2^7*3^2*5*7, 9!=2^7*3^4*5*7, 22!=2^19*3^9*5^4*7^3*11^2*13*17*19.
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MAPLE
| for n from 3 to 10^3 do if sum(floor(n/(2^i)), i=1..15) = prevprime(n+1) then printf(`%d, `, n) fi; od:
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MATHEMATICA
| f[n_] := (t = 0; p = 2; While[s = Floor[n/p]; t = t + s; s > 0, p *= 2]; t); Do[ If[ f[n] == Prime[ PrimePi[n]], Print[n]], {n, 2, 500} ]
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CROSSREFS
| Cf. A011371, A007917.
Sequence in context: A089765 A116030 A116020 * A173743 A035326 A180865
Adjacent sequences: A064390 A064391 A064392 * A064394 A064395 A064396
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KEYWORD
| nonn
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AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), Sep 29 2001
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com) and James A. Sellers (sellersj(AT)math.psu.edu), Oct 01 2001
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