A276685 Between two successive odd digits "a" and "b" there are exactly |a-b| even digits.

1, 0, 2, 3, 4, 6, 5, 8, 20, 21, 10, 22, 24, 26, 29, 9, 28, 7, 40, 42, 30, 25, 44, 32, 41, 11, 12, 23, 33, 34, 45, 46, 36, 48, 27, 60, 50, 43, 38, 61, 14, 62, 64, 47, 66, 52, 63, 68, 16, 80, 65, 54, 67, 70, 49, 82, 72, 69, 84, 74, 85, 55, 56, 83, 86, 18, 88, 200, 76, 89, 90, 87, 77, 78, 202, 201, 100, 204, 206, 92, 208, 58, 220

Offset

1,3

Comments

The sequence is started with a(1) = 1 and always extended with the smallest unused integer not leading to a contradiction.

The sequence is not a permutation of the natural numbers as 31, for instance, will never appear (according to the definition, 31 should show |3-1| = 2 even digits between " 3 " and " 1 " and doesn't).

Links

Jean-Marc Falcoz, Table of n, a(n) for n = 1..10004

Example

Between the first 1 and the first 3 of the sequence, there are indeed |1-3| = 2 even digits (0 and 2).
Between the first 3 and the first 5 of the sequence, there are indeed |3-5| = 2 even digits (4 and 6).
Between the first 5 and the second 1 of the sequence, there are indeed |5-1| = 4 even digits (8,2,0 and 2).
Between the second 1 and the third 1 of the sequence, there are indeed |1-1| = 0 even digits.
Between the third 1 and the first 9 of the sequence, there are indeed |1-9| = 8 even digits (0,2,2,2,4,2,6 and 2).

Crossrefs

Sequence in context: A099884 A191446 A230764 * A225040 A327173 A351412

Adjacent sequences: A276682 A276683 A276684 * A276686 A276687 A276688

Keyword

nonn,base

Author

Eric Angelini and Jean-Marc Falcoz, Sep 13 2016

Status

approved