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 A283433 #31 Apr 29 2019 05:22:34 %S A283433 1,1,4,1,10,76,1,40,1120,67840,1,136,16576,4212736,1073790976,1,544, %T A283433 263680,268779520,274882625536,281475530358784,1,2080,4197376, %U A283433 17184194560,70368756760576,288230393868451840,1180591620768950910976 %N A283433 Triangle read by rows: T(n,m) is the number of pattern classes in the (n,m)-rectangular grid with 4 colors and n>=m, two patterns are in the same class if one of them can be obtained by a reflection or 180-degree rotation of the other. %C A283433 Computed using Burnside's orbit-counting lemma. %H A283433 María Merino, <a href="/A283433/b283433.txt">Rows n=0..41 of triangle, flattened</a> %H A283433 M. Merino and I. Unanue, <a href="https://doi.org/10.1387/ekaia.17851">Counting squared grid patterns with Pólya Theory</a>, EKAIA, 34 (2018), 289-316 (in Basque). %F A283433 For even n and m: T(n,m) = (4^(m*n) + 3*4^(m*n/2))/4; %F A283433 for even n and odd m: T(n,m) = (4^(m*n) + 4^((m*n+n)/2) + 2*4^(m*n/2))/4; %F A283433 for odd n and even m: T(n,m) = (4^(m*n) + 4^((m*n+m)/2) + 2*4^(m*n/2))/4; %F A283433 for odd n and m: T(n,m) = (4^(m*n) + 4^((m*n+n)/2) + 4^((m*n+m)/2) + 4^((m*n+1)/2))/4. %e A283433 Triangle begins: %e A283433 ======================================================================= %e A283433 n\m | 0 1 2 3 4 5 %e A283433 ----|------------------------------------------------------------------ %e A283433 0 | 1 %e A283433 1 | 1 4 %e A283433 2 | 1 10 76 %e A283433 3 | 1 40 1120 67840 %e A283433 4 | 1 136 16576 4212736 1073790976 %e A283433 5 | 1 544 263680 268779520 274882625536 281475530358784 %e A283433 ... %Y A283433 Cf. A225910, A283432. %K A283433 nonn,tabl %O A283433 0,3 %A A283433 _María Merino_, Imanol Unanue, _Yosu Yurramendi_, May 15 2017