

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
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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

JeanMarc 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 JeanMarc Falcoz, Apr 30 2018


STATUS

approved



