A277518 Each even digit k is followed by k odd digits.

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

Offset

1,2

Comments

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.

Links

Jean-Marc Falcoz, Table of n, a(n) for n = 1..4160

Example

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.

Crossrefs

Cf. A277519.

Sequence in context: A082750 A048212 A282864 * A277383 A353730 A077159

Adjacent sequences: A277515 A277516 A277517 * A277519 A277520 A277521

Keyword

nonn,base

Author

Eric Angelini and Jean-Marc Falcoz, Oct 19 2016

Status

approved