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 A166407 #14 May 08 2021 08:35:43 %S A166407 -3,1,0,3,-9,3,0,6,0,3,0,9,-30,1,0,9,0,6,0,12,0,3,0,15,-63,6,0,12,0,9, %T A166407 0,6,0,3,0,21,0,2,0,15,-81,9,0,18,0,6,0,24,0,0,0,15,0,9,0,24,0,6,0,30, %U A166407 -165,6,0,15,0,15,0,6,0,9,0,30,0,0,0,21,0,12,0,30,0,3,0,33,-234,6,0,6 %N A166407 a(n) = floor(3*(A166406(n)/A005408(n))). %C A166407 Conjecture: the quotient A166406(i)/A005408(i) has denominator 3 when i is one of the terms of A166101, and it is integral in other cases. If true, then floor in the formula is unnecessary. %H A166407 Antti Karttunen, <a href="/A166407/b166407.txt">Table of n, a(n) for n = 0..65535</a> %o A166407 (Python) %o A166407 from sympy import floor, jacobi_symbol as J %o A166407 def a(n): %o A166407 l=0 %o A166407 m=0 %o A166407 for i in range(1, 2*n + 2): %o A166407 if J(i, 2*n + 1)==-1: l+=i %o A166407 elif J(i, 2*n + 1)==1: m+=i %o A166407 return floor(3*((l - m)/(2*n + 1))) %o A166407 print([a(n) for n in range(101)]) # _Indranil Ghosh_, Jun 12 2017 %Y A166407 Cf. A166408. %K A166407 sign %O A166407 0,1 %A A166407 _Antti Karttunen_, Oct 21 2009