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 A371222 #29 Mar 19 2024 17:22:58 %S A371222 0,1,2,0,1,2,0,2,1,0,0,0,0,1,2,0,2,1,0,0,0,0,2,1,0,1,2,0,0,0,0,0,0,0, %T A371222 0,0,0,0,0,0,1,2,0,2,1,0,0,0,0,2,1,0,1,2,0,0,0,0,0,0,0,0,0,0,0,0,0,2, %U A371222 1,0,1,2,0,0,0,0,1,2,0,2,1,0,0,0,0,0,0,0,0,0,0,0 %N A371222 Product of digits of (n written in base 3) mod 3. %C A371222 a(A032924(n)) = 1 or 2. For n >= 1, a(A032924(n)) - 1 = A309953(A032924(n)) mod 3 - 1 = A010059(n+1). %F A371222 a(n) = A309953(n) mod 3. %F A371222 a(A081605(n)) = 0. %e A371222 n = 5: 5_10 = 12_3 thus a(5) = 1*2 mod 3 = 2. %e A371222 n = 8: 8_10 = 22_3 thus a(8) = 2*2 mod 3 = 1. %t A371222 a[n_] := Mod[Times @@ IntegerDigits[n, 3], 3]; Array[a, 100, 0] (* _Amiram Eldar_, Mar 18 2024 *) %o A371222 (Python) %o A371222 from functools import reduce %o A371222 from sympy.ntheory import digits %o A371222 def A371222(n): return reduce(lambda a,b: a*b%3,digits(n,3)[1:],1) # _Chai Wah Wu_, Mar 19 2024 %Y A371222 Cf. A007089, A010059, A032924, A081605, A309953, A371281 (base 10). %K A371222 nonn,base %O A371222 0,3 %A A371222 _Ctibor O. Zizka_, Mar 18 2024