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 A368031 #14 Dec 10 2023 15:18:01 %S A368031 1,1,1,3,4,12,23,47,91,202,428,911,1862,3638,6637,11780,20764,36904, %T A368031 64855,111552,186147,302526,479076,739080,1106514,1610045,2278632, %U A368031 3146000,4254002,5682571,7558064,10081716,13532752,18293656,24830210,33733178,45720871 %N A368031 Number of free treelike midpoint-free polycubes of size n, identifying rotations and reflections. %C A368031 Treelike means that the graph connecting midpoints of adjacent cubes has no cycles. %C A368031 Midpoint-free means that no three cubes are in positions (x,y,z), (x+dx,y+dx,z+dz), and (x+2*dx,y+2*dx,z+2*dz). %e A368031 The polycubes for n <= 5 are: %e A368031 n=1: %e A368031 0,0,0 %e A368031 n=2: %e A368031 0,0,0; 0,0,1 %e A368031 n=3: %e A368031 0,0,0; 0,0,1; 0,1,0 %e A368031 n=4: %e A368031 0,0,0; 0,0,1; 0,1,0; 1,0,0 %e A368031 0,0,0; 0,0,1; 0,1,0; 1,0,1 %e A368031 0,0,0; 0,0,1; 0,1,1; 0,1,2 %e A368031 n=5: %e A368031 0,0,0; 0,0,1; 0,1,0; 1,0,1; 1,0,2 %e A368031 0,0,0; 0,0,1; 0,1,0; 1,0,1; 1,1,0 %e A368031 0,0,0; 0,0,1; 0,1,1; 0,1,2; 1,0,1 %e A368031 0,0,0; 0,0,1; 0,1,1; 1,1,1; 1,1,2 %Y A368031 Cf. A304196, A368029. %K A368031 nonn %O A368031 1,4 %A A368031 _Joerg Arndt_, Dec 08 2023