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 A056478 #13 Oct 02 2019 17:45:20
%S A056478 1,1,0,1,1,4,3,14,13,49,46,186,181,714,700,2789,2780,11050,10997,
%T A056478 43946,43895,175259,175088,700074,699875,2798246,2797536,11188856,
%U A056478 11188191,44747434,44744591,178973354,178970560,715860463,715849600,2863377048,2863365834
%N A056478 Number of primitive (aperiodic) palindromic structures using a maximum of four different symbols.
%C A056478 Permuting the symbols will not change the structure.
%D A056478 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 A056478 Andrew Howroyd, <a href="/A056478/b056478.txt">Table of n, a(n) for n = 0..500</a>
%F A056478 a(n) = Sum_{d|n} mu(d)*A124303(ceiling(n/(2*d))) for n > 0.
%F A056478 a(n) = Sum_{k=1..4} A284826(n, k) for n > 0. - _Andrew Howroyd_, Oct 02 2019
%Y A056478 Cf. A007581, A124303, A056460, A284826.
%K A056478 nonn
%O A056478 0,6
%A A056478 _Marks R. Nester_
%E A056478 a(0)=1 prepended and terms a(32) and beyond from _Andrew Howroyd_, Oct 02 2019