Solved after 15335 tries. 16=(1-3+6)*4 17=(1+6)*3-4 18=6/(4/3-1) 19=1+3*4+6 20=(1+3)*6-4 21=(1+4)*3+6 22=(1+3)*4+6 23=1+3*6+4 24=6/(1-3/4) 25=(1+6)*3+4