Table[ n!, {n, 1, 20} ]

mylist = N[ Log[%] ]

lp = ListPlot[ % ];

Fit[ mylist, {1, x, x^2}, x]

fp = Plot[%, {x,0,20} ];

Show[ lp, fp ];

arr = Table[ If[GCD[i,j]==1, 1,0], {i,1,40},{j,1,40}] ;

ListDensityPlot[arr];