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 A065360 #11 Jan 30 2020 06:43:31 %S A065360 1,0,1,1,2,-1,0,0,1,0,1,1,2,0,1,1,2,1,2,2,3,-2,-1,-1,0,-1,0,0,1,-1,0, %T A065360 0,1,0,1,1,2,-1,0,0,1,0,1,1,2,0,1,1,2,1,2,2,3,-1,0,0,1,0,1,1,2,0,1,1, %U A065360 2,1,2,2,3,0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4,-3,-2,-2,-1,-2,-1,-1,0,-2,-1,-1,0,-1,0,0,1,-2,-1,-1,0,-1,0,0 %N A065360 Alternating sum of "negabits". Replace (-2)^k with (-1)^k in negabinary expansion of n. %C A065360 Notation: (-2)[n](-1) %H A065360 Amiram Eldar, <a href="/A065360/b065360.txt">Table of n, a(n) for n = 1..10000</a> %e A065360 6 = 11010 -> +(1)-(1)+(0)-(1)+(0) = -1 = a(6). %o A065360 (PARI) negab(n)=if(n, negab(n\(-2))*10+bittest(n, 0)); \\ A039724 %o A065360 a(n) = my(d=Vecrev(digits(negab(n)))); sum(k=1, #d, d[k]*(-1)^(k-1)); \\ _Michel Marcus_, Aug 28 2019 %Y A065360 Cf. A005351, A039724, A065359. %K A065360 base,easy,sign %O A065360 1,5 %A A065360 _Marc LeBrun_, Oct 31 2001