F(9)=3*F(10)+9+8
F(10)=3*F(11)+10+8
F(11)=3*F(12)+11+8
F(12)=3*F(13)+12+8
F(13)=3*F(14)+13+8
F(14)=3*F(15)+14+8
F(15)=3*F(16)+15+8
F(16)=3*F(17)+16+8
F(17)=3*F(18)+17+8
F(18)=3*F(19)+18+8
F(19)=19
F(18)=3*19+18+8=83
F(17)=3*83+17+8=274
F(16)=3*274+16+8=846
F(15)=3*846+15+8=2561
F(14)=3*2561+14+8=7705
F(13)=3*7705+13+8=23136
F(12)=3*23136+12+8=69428
F(11)=3*69428+11+8=208303
F(10)=3*208303+10+8=624927
F(9)=3*624927+9+8=1874798