A371222 - OEIS

%I #29 Mar 19 2024 17:22:58

%S 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 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 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 Product of digits of (n written in base 3) mod 3.

%C a(A032924(n)) = 1 or 2. For n >= 1, a(A032924(n)) - 1 = A309953(A032924(n)) mod 3 - 1 = A010059(n+1).

%F a(n) = A309953(n) mod 3.

%F a(A081605(n)) = 0.

%e n = 5: 5_10 = 12_3 thus a(5) = 1*2 mod 3 = 2.

%e n = 8: 8_10 = 22_3 thus a(8) = 2*2 mod 3 = 1.

%t a[n_] := Mod[Times @@ IntegerDigits[n, 3], 3]; Array[a, 100, 0] (* _Amiram Eldar_, Mar 18 2024 *)

%o (Python)

%o from functools import reduce

%o from sympy.ntheory import digits

%o def A371222(n): return reduce(lambda a,b: a*b%3,digits(n,3)[1:],1) # _Chai Wah Wu_, Mar 19 2024

%Y Cf. A007089, A010059, A032924, A081605, A309953, A371281 (base 10).

%K nonn,base

%O 0,3

%A _Ctibor O. Zizka_, Mar 18 2024