This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A089400 #11 Jun 13 2025 05:11:13 %S A089400 0,2,2,2,1,4,2,2,1,3,3,3,3,4,2,2,1,3,3,3,2,5,3,3,2,4,4,5,3,4,2,2,1,3, %T A089400 3,3,2,5,3,3,2,4,4,4,4,5,3,3,2,4,4,4,3,6,4,4,3,5,6,5,3,4,2,2,1,3,3,3, %U A089400 2,5,3,3,2,4,4,4,4,5,3,3,2,4,4,4,3,6,4,4,3,5,5,6,4,5,3,3,2,4,4,4,3,6,4,4,3 %N A089400 a(n) = m - A089398(2^m - n) for m>=n. %C A089400 A089398(n) = n-th column sum of binary digits of k*2^(k-1), where summation is over k>=1, without carrying between columns. %F A089400 a(2^k)=1 (for k>1), a(2^k+j)=1+a(j) (for 2^k-k>j>=0), a(2^k-j)=1+A089401(j) (for k>j>0). %e A089400 a(6)=4 since 7 - A089398(2^7 - 6) = 7 - 3 = 4. %Y A089400 Cf. A089398, A089401. %K A089400 nonn %O A089400 0,2 %A A089400 _Paul D. Hanna_, Oct 30 2003