cp's OEIS Frontend

A141836 a(n) = first term that can be reduced in n steps via repeated interpretation of a(n) as a base b+1 number where b is the largest digit of a(n), such that b is always 2 so that each interpretation is base 3. Terms already fully reduced (i.e., single digits) are excluded.

%I A141836 #9 Jul 21 2017 17:30:39
%S A141836 12,202,21111,1001221220,2120202222022022102
%N A141836 a(n) = first term that can be reduced in n steps via repeated interpretation of a(n) as a base b+1 number where b is the largest digit of a(n), such that b is always 2 so that each interpretation is base 3. Terms already fully reduced (i.e., single digits) are excluded.
%C A141836 It is possible to compute additional terms by taking the last term, treating it as base-10 and converting to base-3. This will necessarily create a term which can converted back to base 10 yielding the previous term in the sequence which will itself yield N further terms. But there is no guarantee (except in base 2) that the term so derived will be the first term to produce a sequence of N+1 terms. There could be another, smaller, term which satisfies that requirement but which uses different terms. Pushing the last term of this sequence yields 2120202222022022102 as a possible next term.
%e A141836 a(3) = 21111 because 21111 is the first number that can produce a sequence of three terms by repeated interpretation as a base 3 number: [21111] (base-3) --> [202] (base-3) --> [20] (base-3) --> [6]. Since 6 cannot be interpreted as a base 3 number, the sequence terminates with 20. a(1) = 12 because 12 is the first number that can be reduced once, yielding no further terms interpretable as base 3.
%Y A141836 Cf. A091049, A141837, A141838, A141839, A141840, A141841, A141842.
%K A141836 base,more,nonn
%O A141836 1,1
%A A141836 Chuck Seggelin (seqfan(AT)plastereddragon.com), Jul 10 2008
%E A141836 a(5) from _Giovanni Resta_, Feb 23 2013