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 A345006 #6 Jun 05 2021 16:44:45
%S A345006 1,-1,-1,0,1,1,-2,1,1,-1,0,0,1,-1,-1,2,-1,-1,-1,2,2,-1,-1,-1,2,-1,-1,
%T A345006 0,1,1,-1,0,0,0,0,0,1,-1,-1,0,1,1,-2,1,1,1,-2,-2,1,1,1,-2,1,1,-2,1,1,
%U A345006 1,-2,-2,4,-2,-2,1,1,1,-2,1,1,-2,1,1,1,-2,-2,1,1,1,-2,1,1,-1,0,0,1,-1,-1,2,-1,-1,0,1,1,-1
%N A345006 a(0) = 1; a(3*n) = a(n) + a(n-1), a(3*n+1) = a(3*n+2) = -a(n).
%F A345006 G.f. A(x) satisfies: A(x) = (1 - x - x^2 + x^3) * A(x^3).
%F A345006 G.f.: Product_{k>=0} (1 - x^(3^k) - x^(2*3^k) + x^(3^(k+1))).
%t A345006 a[0] = 1; a[n_] := Switch[Mod[n, 3], 0, a[n/3] + a[(n - 3)/3], 1, -a[(n - 1)/3], 2, -a[(n - 2)/3]]; Table[a[n], {n, 0, 93}]
%t A345006 nmax = 93; A[_] = 1; Do[A[x_] = (1 - x - x^2 + x^3) A[x^3] + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
%t A345006 nmax = 93; CoefficientList[Series[Product[(1 - x^(3^k) - x^(2 3^k) + x^(3^(k + 1))), {k, 0, Floor[Log[3, nmax]] + 1}], {x, 0, nmax}], x]
%Y A345006 Cf. A049347, A054390, A309048, A345007.
%K A345006 sign
%O A345006 0,7
%A A345006 _Ilya Gutkovskiy_, Jun 05 2021