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A105194
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Number of distinct prime factors of the concatenation of two consecutive odd numbers.
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0
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1, 2, 1, 2, 2, 2, 2, 2, 3, 1, 2, 1, 1, 4, 2, 1, 3, 1, 2, 2, 2, 2, 2, 2, 2, 3, 1, 1, 3, 1, 1, 2, 2, 2, 3, 3, 2, 3, 2, 2, 3, 2, 2, 3, 2, 1, 2, 2, 2, 2, 1, 2, 2, 2, 1, 3, 1, 2, 4, 2, 2, 2, 2, 2, 3, 2, 3, 2, 3, 1, 2, 1, 1, 3, 2, 1, 2, 1, 3, 3, 1, 2, 3, 3, 1, 4, 2, 2, 3, 1, 1, 2, 3, 3, 2, 1, 2, 4, 4, 2, 2, 1, 2, 3, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Each odd number is used only once, i.e., although (1,3) and (5,7) are both treated as two consecutive odd numbers, (3,5) and (7,9) are not. [From Harvey P. Dale, Jul 13 2011]
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EXAMPLE
| a(1) =omega(13) = 1; a(2) = omega(57) = 2; a(3) = omega(911) = 1.
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MATHEMATICA
| f[n_]:=PrimeNu[FromDigits[Flatten[IntegerDigits/@{First[n], Last[n]}]]]; f/@Partition[Range[1, 421, 2], 2] (* From Harvey P. Dale, Jul 13 2011 *)
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PROG
| (PARI) a(n)=omega(eval(Str(4*n-3, 4*n-1)))
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CROSSREFS
| Sequence in context: A193386 A068212 A064131 * A008335 A106031 A055175
Adjacent sequences: A105191 A105192 A105193 * A105195 A105196 A105197
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KEYWORD
| nonn,base
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AUTHOR
| Parthasarathy Nambi (PachaNambi(AT)yahoo.com), Apr 11 2005
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EXTENSIONS
| Extended, corrected, and edited by Charles R Greathouse IV (charles.greathouse(AT)case.edu), Apr 27 2010
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