A161920 a(n) = A161511(A004760(n)).

1, 2, 4, 3, 6, 5, 6, 4, 8, 7, 8, 6, 9, 7, 8, 5, 10, 9, 10, 8, 11, 9, 10, 7, 12, 10, 11, 8, 12, 9, 10, 6, 12, 11, 12, 10, 13, 11, 12, 9, 14, 12, 13, 10, 14, 11, 12, 8, 15, 13, 14, 11, 15, 12, 13, 9, 16, 13, 14, 10, 15, 11, 12, 7, 14, 13, 14, 12, 15, 13, 14, 11, 16, 14, 15, 12, 16

Offset: 1

Author

Alford Arnold, Jun 24 2009

Keywords

• nonn

Comments

a(n) gives the one-based position of the first nonzero term on the row n-1 of A126441.

Sequence A016116 can be used to identify the extracted subsequence by computing the number of terms to alternately extract and skip. [This comment is from the original submitter. I don't understand it. - Antti Karttunen, Oct 12 2009]

Crossrefs

a(n) = A161511(A004760(n)) = 1 + A055941(n-1) + A029837(n).

Programs

Python

def A161920(n):
    a, b = 1+(m:=n-1).bit_length(), 1
    for i, j in enumerate(bin(m)[:1:-1], 1):
        if int(j):
            a += i-b
            b += 1
    return a # Chai Wah Wu, Jul 26 2023

Extensions

Edited and extended by Antti Karttunen, Oct 12 2009