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Search: id:A030141
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| A030141 |
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Numbers in which parity of digits alternates. |
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+0
5
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| 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 21, 23, 25, 27, 29, 30, 32, 34, 36, 38, 41, 43, 45, 47, 49, 50, 52, 54, 56, 58, 61, 63, 65, 67, 69, 70, 72, 74, 76, 78, 81, 83, 85, 87, 89, 90, 92, 94, 96, 98, 101, 103, 105, 107, 109, 121, 123, 125, 127, 129
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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An alternating integer is a positive integer for which, in base-10, the parity of its digits alternates.
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REFERENCES
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45th International Mathematical Olympiad (45th IMO), Problem #6 and Solution, Mathematics Magazine, 78 (2005), pp. 247, 250, 251.
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EXAMPLE
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121 is alternating and in the sequence because its consecutive digits are odd-even-odd, 1 being odd and 2 even. Of course, 1234567890 is also alternating.
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CROSSREFS
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Cf. A110303, A110304, A110305.
Sequence in context: A130514 A130232 A103969 this_sequence A064915 A120003 A036965
Adjacent sequences: A030138 A030139 A030140 this_sequence A030142 A030143 A030144
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KEYWORD
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nonn,base
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AUTHOR
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Patrick De Geest (pdg(AT)worldofnumbers.com)
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