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 A054771 #12 May 12 2021 10:13:05 %S A054771 1,3,13,43,129,327,761,1619,3238,6098,10974,18930,31550,50930,80030, %T A054771 122666,183999,270525,390755,555205,777287,1073297,1463583,1972533, %U A054771 2630044,3471508,4539660,5884564,7565868,9652788,12226860,15381924 %N A054771 Number of nonnegative integer 3 X 3 matrices with sum of elements equal to n, up to rotational symmetry. %H A054771 Andrew Howroyd, <a href="/A054771/b054771.txt">Table of n, a(n) for n = 0..1000</a> %F A054771 G.f.: (x^8 - 2*x^7 + 6*x^6 + 2*x^5 + 2*x^4 + 2*x^3 + 6*x^2 - 2*x + 1)/((1 - x^4)^2*(1 - x^2)^2*(1 - x)^5). %Y A054771 Row n=3 of A343874. %Y A054771 Cf. A008610, A054343. %K A054771 easy,nonn %O A054771 0,2 %A A054771 _Vladeta Jovovic_, May 18 2000