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Search: id:A064395
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| A064395 |
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Primes p for which the exponent of the highest power of 2 dividing p! is equal to prevprime(p). |
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+0
1
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| 5, 23, 71, 83, 101, 113, 197, 281, 353, 359, 373, 401, 599, 683, 739, 751, 773, 977, 1091, 1097, 1103, 1217, 1223, 1229, 1237, 1283, 1553, 1559, 1601, 1607, 1619, 2039, 2347, 2357, 2389, 2417, 2473, 2539, 2671, 2699, 2749, 2857, 3019, 3049, 3499, 3581
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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5!=2^3 * 3 * 5, 23!=2^19 * 3^9 * 5^4 * 7^3 * 11^2 * 13 * 17 * 19 * 23, 71!=2^67 * 3^32 * 5^16 * 7^11 * 11^6 * 13^5 * 17^4 * 19^3 * 23^3 * 29^2 * 31^2 * 37 * 41 * 43 * 47 * 53 * 59 * 61 * 67 * 71.
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MAPLE
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for n from 3 to 10^4 do if sum(floor(n/(2^i)), i=1..15) = prevprime(n) and isprime(n) 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[Prime[n]] == Prime[n - 1], Print[ Prime[n]]], {n, 2, 10^3} ]
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CROSSREFS
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Complement of A064393 relative to A064394.
Adjacent sequences: A064392 A064393 A064394 this_sequence A064396 A064397 A064398
Sequence in context: A098498 A106956 A084671 this_sequence A138905 A125955 A103478
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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 James A. Sellers (sellersj(AT)math.psu.edu), Oct 01 2001
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