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 A360498 #11 Dec 30 2023 17:03:27 %S A360498 0,0,4,12,256,3620,87216,2444084,87181220 %N A360498 Number of ways to tile an n X n square using oblongs with distinct dimensions. %C A360498 All possible tilings are counted, including those identical by symmetry. Note that distinct dimensions means that, for example, a 1 x 3 oblong can only be used once, regardless of if it lies horizontally or vertically. %e A360498 a(1) = 0 as no distinct oblongs can tile a square with dimensions 1 x 1. %e A360498 a(2) = 0 as no distinct oblongs can tile a square with dimensions 2 x 2. %e A360498 a(3) = 4. There is one tiling, excluding those equivalent by symmetry: %e A360498 . %e A360498 +---+---+---+ %e A360498 | | %e A360498 +---+---+---+ %e A360498 | | %e A360498 + + %e A360498 | | %e A360498 +---+---+---+ %e A360498 . %e A360498 This tiling can occur in 4 different ways, giving 4 ways in total. %e A360498 a(4) = 12. The possible tilings, excluding those equivalent by symmetry, are: %e A360498 . %e A360498 +---+---+---+---+ +---+---+---+---+ %e A360498 | | | | | %e A360498 + + + +---+---+---+---+ %e A360498 | | | | | %e A360498 +---+---+---+---+ + + %e A360498 | | | | %e A360498 + + + + %e A360498 | | | | %e A360498 +---+---+---+---+ +---+---+---+---+ %e A360498 . %e A360498 The first tiling can occur in 8 different way and the second in 4 different ways, giving 12 ways in total. %Y A360498 Cf. A360499 (rectangles), A004003, A099390, A065072, A233320, A230031. %K A360498 nonn,more %O A360498 1,3 %A A360498 _Scott R. Shannon_, Feb 09 2023