cp's OEIS Frontend

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

%I A377463 #11 Oct 31 2024 01:14:49
%S A377463 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,
%T A377463 33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,
%U A377463 56,57,58,59,60,61,62,63,66,67,70,71,72,73,74,75,76,77,78
%N A377463 Numbers that are not the sum of distinct powers of 4.
%C A377463 Complement of the Moser-de Bruijn sequence (A000695).
%C A377463 Numbers whose base 4 digits contain either 2 or 3.
%o A377463 (Python)
%o A377463 from gmpy2 import digits
%o A377463 def A377463(n):
%o A377463     def f(x):
%o A377463         s = digits(x,4)
%o A377463         for i in range(l:=len(s)):
%o A377463             if s[i]>'1':
%o A377463                 break
%o A377463         else:
%o A377463             return n+int(s,2)
%o A377463         return n-1+(int(s[:i] or '0',2)+1<<l-i)
%o A377463     m, k = n, f(n)
%o A377463     while m != k: m, k = k, f(k)
%o A377463     return m
%o A377463 (Python)
%o A377463 from itertools import count, islice
%o A377463 from gmpy2 import digits
%o A377463 def is_A377463(n): return max(digits(n,4))>'1'
%o A377463 def A377463_gen(): # generator of terms
%o A377463     return filter(is_A377463,count(1))
%o A377463 A377463_list = list(islice(A377463_gen(),50))
%Y A377463 Cf. A000695, A074940 (base 3 analog), A136399 (base 10 analog).
%K A377463 nonn,easy
%O A377463 1,1
%A A377463 _Chai Wah Wu_, Oct 29 2024