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 A055256 #11 Oct 27 2023 22:00:46 %S A055256 1,1,1,1,1,1,2,2,2,3,3,5,4,5,3,4,3,5,3,4,3,5,7,6,4,3,5,7,6,6,7,9,7,10, %T A055256 9,11,11,10,12,11,10,11,14,12,10,11,12,12,11,14,14,17,9,13,14,16,18, %U A055256 12,10,15,15,13,11,15,12,19,15,18,19,19,20,20,18,19,21,20,21,22 %N A055256 Number of odd digits in 3^n. %H A055256 Seiichi Manyama, <a href="/A055256/b055256.txt">Table of n, a(n) for n = 0..10000</a> %o A055256 (PARI) a(n) = #select(x->((x%2) == 1), digits(3^n)); \\ _Michel Marcus_, Nov 22 2019 %Y A055256 Cf. A055255, A034888. %K A055256 nonn,base,easy %O A055256 0,7 %A A055256 _Asher Auel_, May 05 2000