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A277518
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Each even digit k is followed by k odd digits.
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2
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0, 2, 1, 3, 4, 5, 7, 9, 10, 6, 11, 13, 15, 8, 17, 19, 31, 33, 21, 12, 35, 23, 14, 37, 39, 25, 16, 51, 53, 55, 27, 18, 57, 59, 71, 73, 29, 30, 41, 75, 32, 77, 43, 79, 34, 91, 93, 45, 95, 36, 97, 99, 110, 47, 111, 49, 113, 61, 115, 112, 114, 117, 38, 119, 131, 116, 133, 135, 63, 137, 118, 139, 151, 130, 65, 153, 132
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OFFSET
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1,2
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COMMENTS
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The sequence starts with a(1) = 0 and is always extended with the smallest integer not yet present that does not lead to a contradiction.
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LINKS
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EXAMPLE
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As a(1) = 0, we cannot have for a(2) an integer starting with an odd digit; we then extend the sequence with a(2) = 2; this meads that the next 2 digits must be odd; we thus have a(3) = 1 and a(4) = 3, which are the smallest available integers not yet present in the sequence; a(5) = 4 as a(5) cannot start with an odd digit; this value implies that the next 4 digits must be odd; we thus have a(6) = 5, a(7) = 7, a(8) = 9 and a(9) = 10 -- this integer being the smallest available one that doen't lead to a contradiction; a(10) cannot start with an odd digit as the digit "1" in the previous term "10" is already followed by an even digit ("0"); thus a(10) = 6; etc.
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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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STATUS
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approved
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