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 A127252 #7 Aug 04 2023 04:35:39 %S A127252 1,-1,1,1,-1,1,1,-1,1,1,1,-1,1,-1,1,1,-1,1,1,-1,1,-1,1,1,1,-1,1,1,-1, %T A127252 1,1,-1,1,1,1,-1,1,-1,1,1,1,-1,1,1,-1,1,1,-1,1,-1,1,1,-1,1,1,-1,1,1,1, %U A127252 -1,1,-1,1,1,-1,1,1,-1,1,-1,1,1,1,-1,1,1,-1,1,1 %N A127252 Sequence composed of 1 and -1 with the -1's occurring at odious indexed positions given by A091855. %t A127252 a[n_] := If[EvenQ[IntegerExponent[n, 2]] && OddQ[DigitCount[n, 2, 1]], -1, 1]; Array[a, 100, 0] (* _Amiram Eldar_, Aug 04 2023 *) %Y A127252 Row sums of A127251. %Y A127252 Partial sums are A127255. %Y A127252 Cf. A000069, A091855, A127245. %K A127252 sign,base %O A127252 0,1 %A A127252 _Paul Barry_, Jan 10 2007 %E A127252 More terms from _Amiram Eldar_, Aug 04 2023