A377463 Numbers that are not the sum of distinct powers of 4.

2, 3, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 18, 19, 22, 23, 24, 25, 26, 27, 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, 66, 67, 70, 71, 72, 73, 74, 75, 76, 77, 78

Offset: 1

Author

Chai Wah Wu, Oct 29 2024

Keywords

• nonn
• easy

Comments

Complement of the Moser-de Bruijn sequence (A000695).

Numbers whose base 4 digits contain either 2 or 3.

Crossrefs

Cf. A000695, A074940 (base 3 analog), A136399 (base 10 analog).

Programs

Python

from gmpy2 import digits
def A377463(n):
    def f(x):
        s = digits(x,4)
        for i in range(l:=len(s)):
            if s[i]>'1':
                break
        else:
            return n+int(s,2)
        return n-1+(int(s[:i] or '0',2)+1<
				

Python

from itertools import count, islice
from gmpy2 import digits
def is_A377463(n): return max(digits(n,4))>'1'
def A377463_gen(): # generator of terms
    return filter(is_A377463,count(1))
A377463_list = list(islice(A377463_gen(),50))