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 A173343 #27 Jun 02 2025 02:41:35
%S A173343 1,2,0,-5,-8,0,21,34,0,-89,-144,0,377,610,0,-1597,-2584,0,6765,10946,
%T A173343 0,-28657,-46368,0,121393,196418,0,-514229,-832040,0,2178309,3524578,
%U A173343 0,-9227465,-14930352,0,39088169,63245986,0,-165580141,-267914296,0
%N A173343 a(n+4) = a(n+3) - 2*a(n+2) - a(n+1) - a(n).
%C A173343 Sequence appears to give signed Fibonacci numbers, where those Fibonacci numbers "missing" are in A173344. A117647 gives a nonnegative version without zeros. (a(n)) = kjbseq(X) with X = -0.25'i + 0.5'j + 0.5'k + 0.25'i + j' + 0.5k' - 0.25ii - 0.25'jj' - 0.25'kk' + 0.5'ij' + 0.5'ik' - 0.5'ji' -0.25'jk' + 0.25'kj' + 0.25'ee' (see Munafo link for definitions)
%H A173343 C. Dement, <a href="http://fumba.eu/sitelayout/Floretion.html">Online Floretion Multiplier</a> [broken link]
%H A173343 R. J. Mathar, <a href="/A173343/a173343.pdf">Structure of the Floretion Group</a>
%H A173343 R. Munafo, <a href="http://www.mrob.com/pub/math/seq-floretion.html">Sequences Related to Floretions</a>
%H A173343 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1,-2,-1,-1).
%F A173343 G.f.: (x+1)/(x^4+x^3+2*x^2-x+1).
%F A173343 a(n) = b(n)+b(n-1) where b(3n) = b(3n+1) = -b(3n+2) = (-1)^n*A001076(n+1). [From _R. J. Mathar_, Apr 01 2010]
%t A173343 LinearRecurrence[{1,-2,-1,-1},{1,2,0,-5},50] (* _Harvey P. Dale_, Jul 17 2018 *)
%Y A173343 Cf. A173344, A117647.
%K A173343 easy,sign
%O A173343 0,2
%A A173343 _Creighton Dement_, Feb 16 2010