cp's OEIS Frontend

A261231 a(n) = number of steps to reach 0 when starting from k = n and repeatedly applying the map that replaces k with k - (sum of digits in base-3 representation of k).

%I A261231 #16 May 22 2017 20:07:29
%S A261231 0,1,1,2,2,2,3,3,3,4,4,4,5,5,5,6,6,6,7,7,7,8,8,8,8,8,8,9,9,9,10,10,10,
%T A261231 11,11,11,12,12,12,13,13,13,13,13,13,14,14,14,14,14,14,15,15,15,16,16,
%U A261231 16,17,17,17,17,17,17,18,18,18,18,18,18,19,19,19,19,19,19,20,20,20,20,20,20,21,21,21,22,22,22,23,23,23,24,24,24
%N A261231 a(n) = number of steps to reach 0 when starting from k = n and repeatedly applying the map that replaces k with k - (sum of digits in base-3 representation of k).
%H A261231 Antti Karttunen, <a href="/A261231/b261231.txt">Table of n, a(n) for n = 0..19683</a>
%F A261231 a(0) = 0; for n >= 1, a(n) = 1 + a(2*A054861(n)). [Note that A054861(n) = (n - A053735(n))/2, where A053735(n) = sum of digits of n, when written in base 3.]
%o A261231 (Scheme, with memoization-macro definec)
%o A261231 (definec (A261231 n) (if (zero? n) n (+ 1 (A261231 (* 2 (A054861 n))))))
%o A261231 (Python)
%o A261231 from sympy.ntheory.factor_ import digits
%o A261231 def a054861(n): return (n - sum(digits(n, 3)[1:]))/2
%o A261231 def a(n): return 0 if n==0 else 1 + a(2*a054861(n)) # _Indranil Ghosh_, May 22 2017
%Y A261231 Cf. A000244, A053735, A054861, A261232, A261233, A261234, A261235.
%Y A261231 Cf. also A071542.
%K A261231 nonn
%O A261231 0,4
%A A261231 _Antti Karttunen_, Aug 12 2015