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 A072785 #10 Nov 29 2023 06:58:14 %S A072785 0,0,-1,0,0,1,0,0,-1,-1,0,0,0,1,1,0,0,0,-1,-1,-1,0,0,0,0,1,1,1,0,0,0, %T A072785 0,-1,-1,-1,-1,0,0,0,0,0,1,1,1,1,0,0,0,0,0,-1,-1,-1,-1,-1,0,0,0,0,0,0, %U A072785 1,1,1,1,1,0,0,0,0,0,0,-1,-1,-1,-1,-1,-1,0,0,0,0,0,0,0,1,1,1,1,1,1,0,0,0,0,0,0,0,-1,-1,-1,-1,-1,-1,-1,0,0,0,0,0,0,0 %N A072785 Differences between A072781 and A072738. %H A072785 Boris Putievskiy, <a href="http://arxiv.org/abs/1212.2732">Transformations [of] Integer Sequences And Pairing Functions</a>, 2012, arXiv:1212.2732 [math.CO], 2012. %F A072785 From _Boris Putievskiy_, Jan 16 2013: (Start) %F A072785 a(n) = floor((2*A000027(n)-A003056(n)^2-A003056(n))/(A003056(n)+3))*(-1)^A003056(n). %F A072785 a(n) = floor((2*n-t*t-t)/(t+3))*(-1)^t where t=floor((-1+sqrt(8*n-7))/2). %F A072785 (End) %o A072785 (Scheme) (define (A072785 n) (- (A072781 n) (A072738 n))) %Y A072785 Cf. A130517, A162630. %K A072785 sign,tabl %O A072785 0,1 %A A072785 _Antti Karttunen_, Jun 12 2002