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A104543
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Number of distinct prime divisors of 55...559 (with n 5s).
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2
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1, 2, 3, 2, 2, 3, 1, 2, 4, 3, 1, 3, 3, 2, 4, 4, 1, 3, 3, 2, 4, 4, 4, 5, 1, 5, 4, 5, 4, 5, 1, 2, 4, 5, 5, 4, 2, 2, 3, 4, 3, 4, 4, 3, 5, 2, 5, 5, 3, 3, 6, 4, 2, 5, 4, 6, 2, 5, 4, 3, 4, 4, 6, 5, 5, 7, 3, 5, 5, 3, 4, 6, 5, 8, 3, 5, 5, 5, 2, 4, 4, 3, 4, 5, 3, 7, 6
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OFFSET
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1,2
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LINKS
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FORMULA
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EXAMPLE
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The number of distinct prime divisors of 59 is 1 (prime).
The number of distinct prime divisors of 559 is 2.
The number of distinct prime divisors of 5559 is 3.
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MAPLE
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A104543 := proc(n) local x ; x := [9, seq(5, k=1..n)] ; add(op(i, x)*10^(i-1), i=1..nops(x)) ; numtheory[factorset](%) ; nops(%) ; end proc: # R. J. Mathar, Aug 24 2011
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MATHEMATICA
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Table[PrimeNu[(50*10^n + 31)/9], {n, 0, 50}] (* G. C. Greubel, May 10 2017 *)
Table[PrimeNu[FromDigits[PadLeft[{9}, n, 5]]], {n, 2, 90}] (* Harvey P. Dale, Apr 22 2020 *)
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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