This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A117592 #41 Dec 05 2024 19:02:21
%S A117592 1,1,2,1,1,2,2,2,4,1,1,2,1,1,2,2,2,4,2,2,4,2,2,4,4,4,8,1,1,2,1,1,2,2,
%T A117592 2,4,1,1,2,1,1,2,2,2,4,2,2,4,2,2,4,4,4,8,2,2,4,2,2,4,4,4,8,2,2,4,2,2,
%U A117592 4,4,4
%N A117592 a(n) = a(3n) = a(3n+1) = a(3n+2)/2 with a(0)=1.
%C A117592 Row sums of number triangle A117944.
%C A117592 Product of the nonzero digits of (n written in base 3). - _Ilya Gutkovskiy_, Nov 15 2020
%C A117592 a(n) = 1, 2, 4, 8, 16, 32, 64 iff n is respectively in A005836, A023699, A023700, A023701, A023702, A023703, A023704. - _Bernard Schott_, Dec 04 2020
%H A117592 Felix Fröhlich, <a href="/A117592/b117592.txt">Table of n, a(n) for n = 0..10000</a> (first 2001 terms from Vincenzo Librandi)
%F A117592 a(n) = a(3n)/a(0) = a(3n+1)/a(1) = a(3n+2)/a(2).
%F A117592 a(n) = abs(A117942(n)).
%F A117592 G.f. A(x) satisfies: A(x) = (1 + x + 2*x^2) * A(x^3). - _Ilya Gutkovskiy_, Nov 15 2020
%F A117592 a(n) = 2^A081603(n). - _Kevin Ryde_, Nov 15 2020
%t A117592 Nest[ Join[#, #, 2#] &, {1}, 5] (* _Robert G. Wilson v_, Jul 27 2014 *)
%o A117592 (PARI) a(n) = 1 << hammingweight(digits(n,3)>>1); \\ _Kevin Ryde_, Nov 15 2020
%o A117592 (Python)
%o A117592 from gmpy2 import digits
%o A117592 def A117592(n): return 1<<digits(n,3).count('2') # _Chai Wah Wu_, Dec 05 2024
%Y A117592 See A338882 for similar sequences.
%Y A117592 Cf. A081603 (log_2), A117942 (signed), A117944.
%Y A117592 Cf. A005836, A023699, A023700, A023701, A023702, A023703, A023704.
%K A117592 nonn,base
%O A117592 0,3
%A A117592 _Paul Barry_, Apr 05 2006
%E A117592 a(0) = 1 added to the Name by _Bernard Schott_, Dec 04 2020