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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| a(n) = A001221((31+50*10^n)/9). - R. J. Mathar, Aug 24 2011
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EXAMPLE
| 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
| 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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CROSSREFS
| Cf. A104484, A104483.
Sequence in context: A205717 A145390 A128049 * A054988 A143393 A166497
Adjacent sequences: A104540 A104541 A104542 * A104544 A104545 A104546
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KEYWORD
| nonn
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AUTHOR
| Parthasarathy Nambi (PachaNambi(AT)yahoo.com), Apr 20 2005
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