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 A127560 #4 Mar 30 2012 18:34:45 %S A127560 1,0,1,1,0,0,0,1,4,1,0,0,0,0,1,0,1,8,8,1,0,0,0,0,0,0,0,6,6,0,1,12,25, %T A127560 12,1,0,0,0,0,0,0,0,1,1,0,0,18,44,18,0,1,16,50,50,16,1,0,0,0,0,0,0,0, %U A127560 0,0,0,0,8,32,8,0,0,38,155,155,38,0,1,20,82,120,82,20,1 %N A127560 Number of fixed r-celled polyominoes with smallest containing rectangle measuring k by m, read in order r=A056556(n)+1, k=A056560(n)+1, m=A056558(n)+1. %C A127560 The sum of each triangle, i.e. for a given r the sum of a(n) for all n such that r=A056556(n)+1 is the number of r-celled fixed polyominoes, A001168(r). %e A127560 The 5th triangle of the sequence, the number of fixed pentominoes by dimension, is %e A127560 0,0,0,0,1 %e A127560 0,0,6,12 %e A127560 0,6,25 %e A127560 0,12 %e A127560 1 %e A127560 This indicates, for example, there are 25 fixed pentominos that fit in a 3 X 3 rectangle and 12 fixed pentominos that fit in a 4 X 2 rectangle. %Y A127560 Cf. A000105, A000988, A001168 Indices for reading by triangles given by A056556, A056560, A056558. %K A127560 nonn %O A127560 0,9 %A A127560 _Graeme McRae_, Jan 18 2007