Coloring a circuit with 4 colors.

Terms

a(0) =1a(1) =1a(2) =4a(3) =10a(4) =31a(5) =91a(6) =274a(7) =820a(8) =2461a(9) =7381a(10) =22144a(11) =66430a(12) =199291a(13) =597871a(14) =1793614a(15) =5380840a(16) =16142521a(17) =48427561a(18) =145282684a(19) =435848050a(20) =1307544151a(21) =3922632451a(22) =11767897354a(23) =35303692060a(24) =105911076181a(25) =317733228541a(26) =953199685624