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 A137672 #19 Jul 27 2023 09:48:40 %S A137672 1,1,1,2,1,1,2,1,2,2,1,3,1,1,2,2,2,3,1,2,1,3,2,2,2,3,1,2,2,3,2,3,2,4, %T A137672 1,3,3,1,3,2,1,4,1,1,2,2,2,3,2,2,3,3,2,3,3,3,4,2,4,1,2,2,3,1,3,2,3,2, %U A137672 4,2,3,3,2,4,2,4,3,3,3,4,1,2,5,1,3,2,1,3,3,3,4,2,2,2,3,3,4,2,2,3,4,3,5,1,4 %N A137672 Number of ones in binary representation of A137671(n). %H A137672 Reinhard Zumkeller, <a href="/A137672/b137672.txt">Table of n, a(n) for n = 1..10000</a> %F A137672 a(n) = A000120(A137671(n)). %F A137672 a(A137674(n)) = 1. %F A137672 a(A137674(n)-1) = n-1. %t A137672 b[1] = 1; b[n_] := b[n] = Count[Array[a, n-1], a[n-1]]; a[n_] := a[n] = DigitCount[b[n], 2, 1]; Array[a, 100] (* _Amiram Eldar_, Jul 27 2023 *) %Y A137672 Cf. A000120, A137671, A137674. %K A137672 nonn,base %O A137672 1,4 %A A137672 _Reinhard Zumkeller_, Feb 05 2008