A161920 - OEIS

%I #11 Jul 26 2023 21:01:48

%S 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,

%T 10,6,12,11,12,10,13,11,12,9,14,12,13,10,14,11,12,8,15,13,14,11,15,12,

%U 13,9,16,13,14,10,15,11,12,7,14,13,14,12,15,13,14,11,16,14,15,12,16

%N a(n) = A161511(A004760(n)).

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

%C 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]

%o (Python)

%o def A161920(n):

%o     a, b = 1+(m:=n-1).bit_length(), 1

%o     for i, j in enumerate(bin(m)[:1:-1], 1):

%o         if int(j):

%o             a += i-b

%o             b += 1

%o     return a # _Chai Wah Wu_, Jul 26 2023

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

%K nonn

%O 1,2

%A _Alford Arnold_, Jun 24 2009

%E Edited and extended by _Antti Karttunen_, Oct 12 2009