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A105248
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Number of distinct prime divisors of 88...887 (with n 8's).
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1
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1, 2, 1, 1, 2, 1, 3, 3, 1, 2, 3, 1, 3, 4, 4, 4, 4, 2, 3, 3, 4, 3, 2, 3, 2, 2, 3, 5, 5, 4, 3, 4, 2, 5, 6, 2, 5, 3, 2, 3, 3, 3, 3, 3, 4, 2, 4, 2, 5, 2, 3, 5, 3, 6, 4, 5, 2, 5, 4, 3, 3, 3, 4, 2, 5, 4, 4, 5, 5, 4, 5, 1, 3, 6, 4, 2, 2, 4, 3, 4, 5, 7, 6, 5, 4, 8, 4
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OFFSET
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0,2
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LINKS
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Amiram Eldar, Table of n, a(n) for n = 0..199
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FORMULA
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a(n) = A001221(A173812(n+1)). - Michel Marcus, Jan 27 2014
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EXAMPLE
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The number of distinct prime divisors of 87 is 2.
The number of distinct prime divisors of 887 is 1 (prime).
The number of distinct prime divisors of 8887 is 1 (prime).
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MATHEMATICA
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Table[PrimeNu[(8*10^(n + 1) - 17)/9], {n, 1, 50}] (* G. C. Greubel, May 21 2017 *)
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PROG
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a(n) = omega((8*10^(n+1)-17)/9); \\ Michel Marcus, Jan 27 2014
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CROSSREFS
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Cf. A104524, A104889.
Sequence in context: A236480 A236508 A239000 * A289495 A076302 A104524
Adjacent sequences: A105245 A105246 A105247 * A105249 A105250 A105251
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KEYWORD
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nonn,base
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AUTHOR
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Parthasarathy Nambi, Apr 29 2005
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EXTENSIONS
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More terms from Brian Lauer (bel136(AT)psu.edu), Feb 23 2006
Corrected and extended by Michel Marcus, Jan 27 2014
More terms from Amiram Eldar, Jan 27 2020
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STATUS
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approved
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