OFFSET
1,1
COMMENTS
The "Erase or triple" protocol describes how to transform an integer K into an integer L: if K has 2 or more identical digits, erase them to get L (1201331 becomes 20); if K has no duplicate digits, triple K to get L (20 becomes 60). Some integers disappear immediately (like 1100 or 9191), other disappear if you apply this protocol to the successive results. This sequence gathers them all.
Note that 1102 is transformed into 2 because no leading zeroes are admitted.
LINKS
Jean-Marc Falcoz, Table of n, a(n) for n = 1..33333
EXAMPLE
2 becomes 6 (the triple of 2), then 6 becomes 18 (the triple of 6), then 18 becomes 54 (the triple of 18) and now 162, 486, 1458, 4374, 37 (because the pair 4-4 is erased), 111 (the triple of 37), ... and disappearance.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Eric Angelini and Jean-Marc Falcoz, Feb 26 2018
STATUS
approved