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 A089263 #15 Sep 27 2018 17:54:53 %S A089263 0,0,1,-1,2,-1,0,-1,3,-1,0,-1,1,-1,0,-1,4,-1,0,-1,1,-1,0,-1,2,-1,0,-1, %T A089263 1,-1,0,-1,5,-1,0,-1,1,-1,0,-1,2,-1,0,-1,1,-1,0,-1,3,-1,0,-1,1,-1,0, %U A089263 -1,2,-1,0,-1,1,-1,0,-1,6,-1,0,-1,1,-1,0,-1,2,-1,0,-1,1,-1 %N A089263 First differences of A080791. %C A089263 Number of trailing zeros in the binary representation of n, minus one if n is not a power of two. %C A089263 a(0) = 0 by convention. - _Antti Karttunen_, Sep 27 2018 %H A089263 Antti Karttunen, <a href="/A089263/b089263.txt">Table of n, a(n) for n = 0..65537</a> %H A089263 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a> %F A089263 a(0)=0, a(2n) = a(n) + 1, a(2n+1) = -1 + [n==0]. %F A089263 a(n) = A007814(n) + A036987(n-1) - 1. %F A089263 G.f.: sum(k>=0, t^2/(1+t), t=x^2^k). %F A089263 a(n) = A080791(n+1) - A080791(n). - _Antti Karttunen_, Sep 27 2018 %o A089263 (PARI) a(n)=if(!n,n,(valuation(n, 2)+(2^valuation(n, 2)==n)-1)); \\ Check for n=0 added by _Antti Karttunen_, Sep 27 2018 %o A089263 (PARI) a(n)=if(n<1,0,if(n%2==0,a(n/2)+1,-1+(((n-1)/2)==0))) %Y A089263 Cf. A080791, A088705. %K A089263 sign,easy %O A089263 0,5 %A A089263 _Ralf Stephan_, Oct 30 2003 %E A089263 Definition corrected (A023416 replaced with A080791) by _Antti Karttunen_, Sep 27 2018