OFFSET
1,1
COMMENTS
This is the lexicographically earliest sequence of distinct positive terms with this property.
MAPLE
a(1) = 10 is in the sequence because the absolute difference between 1 and 0 is 1, and 1 is a subchain of 10;
a(2) = 12 is in the sequence because the absolute difference between 1 and 2 is 1, and 1 is a subchain of 12;
a(3) = 20 is in the sequence because the absolute difference between 2 and 0 is 2, and 2 is a subchain of 20;
...
a(20) = 124; the absolute difference between 1 and 2 is 1; the absolute difference between 2 and 4 is 2; concatenating those differences produce 12 and 12 is a subchain of 124; etc.
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Eric Angelini, Nov 12 2020
STATUS
approved