A376919 The nonpowers of 3.

0, 2, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70

Offset: 0

Author

Chai Wah Wu, Oct 10 2024

Keywords

• nonn

Comments

Complement of A000244. Numbers whose sum of digits in base 3 is not equal to 1.

Crossrefs

Cf. A057716, A057717, A000244.

Programs

Mathematica

Complement[Range[0,70],Table[3^n, {n, 0, 3}]] (* James C. McMahon, Oct 18 2024 *)

Python

from sympy import integer_log
def A376919(n): return n+(m:=integer_log(n,3)[0]+1)+(n+m>=3**m) if n else 0

Formula

For n > 0, a(n) = n + floor(log_3(n)) + 2 if n + floor(log_3(n)) + 1 >= 3^(floor(log_3(n)) + 1) and a(n) = n + floor(log_3(n)) + 1 otherwise.