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A048288
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Number of prime factors counted with multiplicity of the reverse concatenation of numbers from 1 to n.
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11
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0, 2, 2, 2, 3, 2, 2, 4, 5, 3, 2, 3, 3, 4, 6, 4, 7, 10, 4, 5, 4, 5, 4, 5, 6, 9, 9, 5, 7, 8, 3, 6, 5, 7, 9, 8, 4, 3, 6, 5, 8, 6, 3, 8, 7, 5, 7, 7, 3, 6, 3, 7, 12, 14, 3, 5, 4, 6, 3, 3, 5, 9, 6, 6, 7, 7, 4, 8, 8, 4, 9, 5, 7, 8, 10, 3, 7, 6, 4, 9, 10, 1, 3, 8, 3
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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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21 = 3*7 so a(2) = 2; 321 = 3*107 so a(3) = 2; 4321 = 29*149 so a(4) = 2; etc.
a(1)=0 since 1 has no prime factors.
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MATHEMATICA
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Join[{0}, Table[PrimeOmega[FromDigits[Flatten[IntegerDigits[Range[i, 1, -1]]]]], {i, 2, 36}]] (* Jayanta Basu, May 30 2013 *)
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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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Paul Jasper (jasperpaul(AT)hotmail.com)
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EXTENSIONS
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Offset and a(19) corrected and more terms from Sean A. Irvine, Jun 13 2021
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STATUS
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approved
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