OFFSET
1,2
COMMENTS
The sequence starts with a(1) = 1 and is always extended with the smallest positive integer not yet present that does not lead to a contradiction.
EXAMPLE
a(1) = 1 forces the next digit to be a 1 (as odd digits must come in pairs); the smallest positive integer not yet present that starts with a 1 and does not lead to a contradiction is 10. Thus, a(2) = 10;
a(3) = 2 as the smallest positive integer not yet present that does not lead to a contradiction is 2;
a(4) = 3 as the smallest positive integer not yet present that does not lead to a contradiction is 3;
a(5) = 30 as a(5) must start with a 3 (the odd digits must come in pairs) and 30 is the smallest positive integer not yet present that does not lead to a contradiction; etc.
PROG
(Python) # see A342076 for aupton, pairsup
mustpair = {1, 3, 5, 7, 9}
print(aupton(67)) # Michael S. Branicky, Feb 28 2021
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Eric Angelini, Feb 28 2021
STATUS
approved