cp's OEIS Frontend

A091047 a(n) = the final value of n reached through repeated interpretation of n as a base b+1 number where b is the largest digit of n.

%I A091047 #9 Jun 08 2025 16:15:42
%S A091047 1,2,3,4,5,6,7,8,9,2,3,5,7,9,3,7,3,3,19,6,7,8,3,9,3,6,3,6,29,5,7,9,3,
%T A091047 19,3,3,7,3,39,6,7,8,3,9,29,19,39,9,49,5,7,9,3,19,3,7,39,3,59,8,3,9,
%U A091047 29,19,39,9,3,9,69,7,39,3,59,8,3,9,29,39,79,3,59,8,3,9,29,39,79,3,89,90,91,92
%N A091047 a(n) = the final value of n reached through repeated interpretation of n as a base b+1 number where b is the largest digit of n.
%C A091047 Any value of n with at least one digit 9 will not reduce further since 9+1 is 10 and n in base 10 is n. Also any single-digit number will likewise not reduce further. Many terms reduce in very few steps and others take longer (88 for example, takes 8 steps). See A091048 for the number of steps for each value of n. There is no maximum number of steps. See A091049 to see the first term requiring n steps.
%H A091047 C. Seggelin, <a href="http://www.plastereddragon.com/maths/bases.htm">Interesting Base Conversions</a>.
%e A091047 a(18)=3 because 18 in base 9 is 17. 17 in base 8 is 15. 15 in base 6 is 11. 11 in base 2 is 3. 3 does not reduce further because 3 in base 4 is 3. Thus 18 reduces to 3 in 4 steps.
%Y A091047 Cf. A054055 (largest digit of n) A068505 (n as base b+1 number where b=largest digit of n) A091048 (number of times n must be interpreted as a base b+1 number where b is the largest digit of n until an unchanging value is reached) A091049 (a(n) = first term which reduces to an unchanging value in n steps via repeated interpretation of a(n) as a base b+1 number where b is the largest digit of a(n)).
%K A091047 base,nonn
%O A091047 1,2
%A A091047 _Chuck Seggelin_, Dec 15 2003