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 A056470 #15 Dec 16 2017 11:28:47
%S A056470 1,1,2,2,5,5,15,15,52,52,202,202,855,855,3845,3845,18002,18002,86472,
%T A056470 86472,422005,422005,2079475,2079475,10306752,10306752,51263942,
%U A056470 51263942,255514355,255514355,1275163905
%N A056470 Number of palindromic structures using a maximum of five different symbols.
%C A056470 Permuting the symbols will not change the structure.
%D A056470 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 A056470 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (1,10,-10,-31,31,30,-30).
%F A056470 a(2n-1) = a(2n) = A056272(n). [R. J. Mathar, Nov 24 2010]
%F A056470 G.f.: -x*(19*x^6-24*x^4+9*x^2-1) / ((x-1)*(2*x^2-1)*(3*x^2-1)*(5*x^2-1)). [_Colin Barker_, Dec 05 2012]
%t A056470 LinearRecurrence[{1,10,-10,-31,31,30,-30},{1,1,2,2,5,5,15},40] (* _Harvey P. Dale_, Dec 16 2017 *)
%Y A056470 Cf. A056451.
%K A056470 nonn,easy
%O A056470 1,3
%A A056470 _Marks R. Nester_