OFFSET
1,2
COMMENTS
The sequence starts with a(1) = 1 and was always extended with the smallest integer not yet present and not leading to a contradiction.
From Robert G. Wilson v, Feb 07 2018: (Start)
Inverse: 1, 6, 10, 12, 14, 16, 18, 20, 2, 4, 7, 8, 9, 11, 13, 15, 17, 19, 3, ..., .
Permutation of the Integers.
(End)
LINKS
Jean-Marc Falcoz, Table of n, a(n) for n = 1..10001
EXAMPLE
The "0" of 10 is strictly < "1", which is the largest digit of 1;
The "0" of 20 is strictly < "1", which is the largest digit of 10;
The "1" of 11 is strictly < "2", which is the largest digit of 20;
The "0" of 30 is strictly < "1", which is the largest digit of 11;
The "2" of 2 is strictly < "3", which is the largest digit of 30;
The "1" of 12 is strictly < "2", which is the largest digit of 2; etc.
MATHEMATICA
f[s_List] := Block[{k = 1, mx = Max@IntegerDigits@s[[-1]]}, While[MemberQ[s, k] || Min@IntegerDigits@k >= mx, k++]; Append[s, k]]; Nest[f, {1}, 80] (* Robert G. Wilson v, Feb 07 2018 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Eric Angelini and Jean-Marc Falcoz, Feb 07 2018
STATUS
approved