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 A343875 #8 Jan 02 2022 18:31:16
%S A343875 1,0,1,0,1,1,0,1,1,1,0,1,3,3,1,0,1,4,11,3,1,0,1,8,31,24,6,1,0,1,10,84,
%T A343875 113,55,6,1,0,1,16,198,528,410,99,10,1,0,1,20,440,2003,2710,1091,181,
%U A343875 10,1,0,1,29,904,6968,15233,10488,2722,288,15,1,0,1,35,1766,21593,75258,82704,34399,5806,461,15,1
%N A343875 Array read by antidiagonals: T(n,k) is the number of n X n nonnegative integer matrices with sum of elements equal to k, up to rotations and reflections.
%H A343875 Andrew Howroyd, <a href="/A343875/b343875.txt">Table of n, a(n) for n = 0..1325</a>
%e A343875 Array begins:
%e A343875 =====================================================
%e A343875 n\k | 0 1 2 3 4 5 6 7
%e A343875 ----+------------------------------------------------
%e A343875 0 | 1 0 0 0 0 0 0 0 ...
%e A343875 1 | 1 1 1 1 1 1 1 1 ...
%e A343875 2 | 1 1 3 4 8 10 16 20 ...
%e A343875 3 | 1 3 11 31 84 198 440 904 ...
%e A343875 4 | 1 3 24 113 528 2003 6968 21593 ...
%e A343875 5 | 1 6 55 410 2710 15233 75258 331063 ...
%e A343875 6 | 1 6 99 1091 10488 82704 563864 3376134 ...
%e A343875 7 | 1 10 181 2722 34399 360676 3235551 25387944 ...
%e A343875 ...
%o A343875 (PARI)
%o A343875 U(n,s) = {(s(1)^(n^2) + s(1)^(n%2)*(2*s(4)^(n^2\4) + s(2)^(n^2\2)) + 2*s(1)^n*s(2)^(n*(n-1)/2) + 2*(s(1)^(n%2)*s(2)^(n\2))^n )/8}
%o A343875 T(n,k)={polcoef(U(n,i->1/(1-x^i) + O(x*x^k)), k)}
%Y A343875 Rows n=0..3 are A000007, A000012, A005232, A054343.
%Y A343875 Columns 0..1 are A000012, A008805(n-1).
%Y A343875 Cf. A054252 (binary case), A318795, A343097, A343874.
%K A343875 nonn,tabl
%O A343875 0,13
%A A343875 _Andrew Howroyd_, May 06 2021