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 A303785 Lexicographically earliest sequence of distinct terms such that what emerges from the mask is odd (see the Comment section for the mask explanation). 6
 1, 11, 2, 13, 3, 15, 4, 17, 5, 19, 6, 21, 7, 23, 8, 25, 9, 27, 101, 10, 103, 12, 105, 14, 107, 16, 109, 18, 111, 20, 113, 22, 115, 24, 117, 26, 119, 28, 121, 29, 123, 30, 125, 31, 127, 32, 129, 33, 131, 34, 133, 35, 135, 36, 137, 37, 139, 38, 141, 39, 143, 40, 145, 41, 147, 42, 149, 43, 151, 44, 153, 45, 155, 46, 157, 47 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For any pair of contiguous terms, one of the terms uses fewer digits than the other. This term is called the mask. Put the mask on the other term, starting from the left. What is not covered by the mask forms an odd number. The sequence starts with a(1) = 1 and is always extended with the smallest integer not yet present that doesn't lead to a contradiction. This sequence is a permutation of the integers > 0, as all integers will appear at some point, either as mask or masked. LINKS Jean-Marc Falcoz, Table of n, a(n) for n = 1..10001 EXAMPLE In the pair (1,11), 1 is the mask; 1 emerges and is odd; In the pair (11,2), 2 is the mask; 1 emerges and is odd; In the pair (2,13), 2 is the mask; 3 emerges and is odd; In the pair (13,3), 3 is the mask; 3 emerges and is odd; ... In the pair (11019,2018), 2018 is the mask; 9 emerges and is odd; etc. CROSSREFS Cf. A303782 (same idea with primes), A303783 (with squares), A303784 (with even numbers), A303786 (rebuilds the sequence itself term by term). Sequence in context: A323484 A318927 A267320 * A262369 A092260 A318926 Adjacent sequences:  A303782 A303783 A303784 * A303786 A303787 A303788 KEYWORD nonn,base AUTHOR Eric Angelini and Jean-Marc Falcoz, Apr 30 2018 STATUS approved

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Last modified February 26 18:29 EST 2020. Contains 332293 sequences. (Running on oeis4.)