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A104186
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Number of distinct prime divisors of numbers from four consecutive concatenated odd numbers.
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2
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2, 2, 2, 2, 3, 3, 3, 2, 2, 4, 2, 1, 3, 3, 2, 2, 3, 2, 2, 4, 3, 2, 4, 2, 2, 3, 3, 4, 4, 3, 2, 4, 3, 2, 5, 2, 2, 4, 1, 3, 3, 4, 2, 3, 3, 2, 3, 3, 3, 4, 3, 3, 2, 3, 5, 3, 3, 1, 4, 4, 2, 4, 2, 2, 5, 2, 4, 3, 3, 3, 3, 4, 2, 4, 3, 2, 3, 2, 2, 3, 4, 3, 3, 2, 3, 6, 4
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OFFSET
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1,1
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COMMENTS
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Interestingly, 23252729 is prime.
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LINKS
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EXAMPLE
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The number of distinct prime factors of 1357 is 2 - the first term in the sequence.
The number of distinct prime factors of 3579 is 2 - the second term in the sequence.
The number of distinct prime factors of 57911 is 2 - the third term in the sequence.
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MATHEMATICA
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a[n_] := PrimeNu@ FromDigits @ (Join @@ IntegerDigits /@ (2*n + {-1, 1, 3, 5})); Array[a, 100] (* Amiram Eldar, Jan 27 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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Offset corrected and more terms added by Amiram Eldar, Jan 27 2020
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STATUS
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approved
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