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 A056477 #12 Oct 02 2019 17:14:43
%S A056477 1,1,0,1,1,4,3,13,12,39,36,121,116,364,351,1088,1080,3280,3237,9841,
%T A056477 9800,29510,29403,88573,88440,265716,265356,797121,796796,2391484,
%U A056477 2390352,7174453,7173360,21523238,21520080,64570064,64566684,193710244,193700403,581130368,581120880
%N A056477 Number of primitive (aperiodic) palindromic structures using a maximum of three different symbols.
%C A056477 Permuting the symbols will not change the structure.
%D A056477 M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]
%H A056477 Andrew Howroyd, <a href="/A056477/b056477.txt">Table of n, a(n) for n = 0..500</a>
%F A056477 a(n) = Sum_{d|n} mu(d)*A124302(ceiling(n/(2*d))) for n > 0.
%F A056477 a(n) = Sum_{k=1..3} A284826(n, k) for n > 0. - _Andrew Howroyd_, Oct 02 2019
%Y A056477 Cf. A007051, A124302, A056459, A284826.
%K A056477 nonn
%O A056477 0,6
%A A056477 _Marks R. Nester_
%E A056477 a(0)=1 prepended and terms a(32) and beyond from _Andrew Howroyd_, Oct 02 2019