cp's OEIS Frontend

A261923 Number of steps to reach 0, starting at n, and iteration the map x -> A261922(x).

%I A261923 #19 Sep 21 2023 11:10:20
%S A261923 0,1,2,1,2,2,3,1,2,2,2,3,3,3,3,1,2,2,2,3,2,2,3,3,3,3,3,3,3,3,3,1,2,2,
%T A261923 2,3,2,2,3,3,2,2,2,3,2,3,3,3,3,3,3,3,2,3,3,3,3,3,3,3,3,3,3,1,2,2,2,3,
%U A261923 2,2,3,3,2,2,2,4,3,2,3,3,2,2,2,4,2,2
%N A261923 Number of steps to reach 0, starting at n, and iteration the map x -> A261922(x).
%H A261923 Reinhard Zumkeller, <a href="/A261923/b261923.txt">Table of n, a(n) for n = 0..10000</a>
%F A261923 a(A262279(n)) = n. - _Reinhard Zumkeller_, Sep 17 2015
%e A261923 13 -> 4 -> 3 -> 0, which takes 3 steps to reach 0, so a(13)=3.
%o A261923 (Haskell)
%o A261923 a261923 n = fst $ until ((== 0) . snd)
%o A261923                         (\(step, x) -> (step + 1, a261922 x)) (0, n)
%o A261923 -- _Reinhard Zumkeller_, Sep 17 2015
%o A261923 (PARI) a(n) = if (n==0, 0, my(k=1, x=A261922(n)); while (x, x=A261922(x); k++); k); \\ _Michel Marcus_, Sep 20 2023
%o A261923 (Python)
%o A261923 def f(n): b=bin(n)[2:]; return next(k for k in range(2**len(b)) if bin(k)[2:] not in b)
%o A261923 def a(n): return 0 if n == 0 else 1 + a(f(n))
%o A261923 print([a(n) for n in range(99)]) # _Michael S. Branicky_, Sep 21 2023
%Y A261923 Cf. A261922, A261461, A262279.
%K A261923 nonn
%O A261923 0,3
%A A261923 _N. J. A. Sloane_, Sep 17 2015