OFFSET
1,1
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..10000
J. H. Conway and N. J. A. Sloane, Lexicographic codes: error-correcting codes from game theory, IEEE Transactions on Information Theory, 32:337-348, 1986.
EXAMPLE
a(1) = 10 by definition.
a(2) = 21 because '2' has not yet appeared in the tens place and '1' has not yet appeared in the ones place.
PROG
(Python)
def ham(m, n):
s, t = str(min(m, n))[::-1], str(max(m, n))[::-1]
return len(t) - len(s) + sum(s[i] != t[i] for i in range(len(s)))
def aupton(terms):
alst = [10]
for n in range(2, terms+1):
an = alst[-1] + 1
while any(ham(an, aprev) < 2 for aprev in alst[::-1]): an += 1
alst.append(an)
return alst
print(aupton(60)) # Michael S. Branicky, Jul 22 2021
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Peter Woodward, Jul 11 2021
EXTENSIONS
Edited and corrected by N. J. A. Sloane, Jul 20 2021
STATUS
approved