A189822 Positions of 1 in A189820; complement of A003278.

3, 6, 7, 8, 9, 12, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 30, 33, 34, 35, 36, 39, 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, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 84

Offset: 1

Author

Clark Kimberling, Apr 28 2011

Keywords

• nonn
• easy

Links

• G. C. Greubel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A081610, A189820, A003278.

Programs

Mathematica

a[1] = 0; h = 50;
Table[a[3 k - 2] = a[k], {k, 1, h}];
Table[a[3 k - 1] = a[k], {k, 1, h}];
Table[a[3 k] = 1, {k, 1, h}];
Flatten[Position[%%, 1]]

Python

from gmpy2 import digits
def A189822(n):
    def f(x):
        l = (s:=digits(x-1,3)).find('2')
        if l >= 0: s = s[:l]+'1'*(len(s)-l)
        return n+1+int(s,2)
    m, k = n, f(n)
    while m != k: m, k = k, f(k)
    return m # Chai Wah Wu, Dec 05 2024