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Search: id:A064393
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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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+0
2
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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; listen)
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OFFSET
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0,1
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COMMENT
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[n/2]+[n/4]+[n/8]+[n/16]+... = prevprime(n+1).
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EXAMPLE
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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
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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
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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
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Cf. A011371, A007917.
Sequence in context: A089765 A116030 A116020 this_sequence A035326 A063907 A056166
Adjacent sequences: A064390 A064391 A064392 this_sequence A064394 A064395 A064396
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KEYWORD
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nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu), Sep 29 2001
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EXTENSIONS
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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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