cp's OEIS Frontend

A141839 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 5 so that each interpretation is base 6. Terms already fully reduced (i.e., single digits) are excluded.

%I A141839 #9 Jul 21 2017 12:40:39
%S A141839 15,55,325,32501,410245,145055113,305344340421
%N A141839 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 5 so that each interpretation is base 6. Terms already fully reduced (i.e., single digits) are excluded.
%C A141839 It is sometimes possible to compute additional terms by taking the last term, treating it as base 10 and converting to base 6. This may create a term minimally interpretable as base 6 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 does not produce a value minimally interpretable as base 6.
%e A141839 a(3) = 325 because 325 is the first number that can produce a sequence of three terms by repeated interpretation as a base 6 number: [325] (base-6) --> [125] (base-6) --> [53] (base-6) --> [33]. Since 33 cannot be interpreted as a base 6 number, the sequence terminates with 53. a(1) = 15 because 15 is the first number that can be reduced once, yielding no further terms minimally interpretable as base 6.
%Y A141839 Cf. A091049, A141836, A141837, A141838, A141840, A141841, A141842.
%K A141839 base,more,nonn
%O A141839 1,1
%A A141839 Chuck Seggelin (seqfan(AT)plastereddragon.com), Jul 10 2008
%E A141839 a(7) from _Giovanni Resta_, Feb 23 2013