I got the LeWitt set comprehensions wrong. I’ve fixed the others (I edited this blog without declaring it, I feel unclean…) but the 4 line, 4 colour one was a bit harder. Here’s a sketch for the fixed version. C = {r,y,b,k} L = {|, , /, -} V = C x L = {(r, |), … (k, -)} W = PV = {{(r, |)}, .. {(r, |), … (k, -)}} X = {x :∈ W | #x > 0 ^ #x < 5} % All sets of 1..4 Y = {x :∈ X | #x = # U (U x) } % All sets with unique first pair items Z = {x :∈ Y, y :∈ x • U (U y)} % Each item of each member set combined Alternative Z:Z = {x :∈ Y • U (U x)} % Each member set combined