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 A090047 #12 Jul 28 2025 03:13:55 %S A090047 1,0,2,2,4,2,2,3,6,3,2,2,4,2,3,4,8,4,3,2,4,2,2,4,6,3,2,2,4,2,4,5,10,5, %T A090047 4,2,4,2,2,3,6,3,2,2,4,2,4,4,8,4,3,3,4,2,2,3,6,3,2,2,4,3,5,6,12,6,5,3, %U A090047 4,2,2,3,6,3,2,2,4,2,3,4,8,4,3,2,4,4,2,3,6,3,2,6,4,4,4,5,10,5,4,2,4,2 %N A090047 Length of longest contiguous block of 0's in binary expansion of n^2. %H A090047 Amiram Eldar, <a href="/A090047/b090047.txt">Table of n, a(n) for n = 0..10000</a> %F A090047 a(n) = A087117(A000290(n)). %t A090047 a[n_] := If[n <= 1, 1-n, Max[Length /@ Split[IntegerDigits[n^2, 2]][[2 ;; -1 ;; 2]]]]; Array[a, 100, 0] (* _Amiram Eldar_, Jul 28 2025 *) %Y A090047 Cf. A000290, A023416, A087117, A090001, A090046, A090048, A090049. %K A090047 nonn,base %O A090047 0,3 %A A090047 _Reinhard Zumkeller_, Nov 20 2003