E-trees with at most 3 colors.

Terms

a(0) =1a(1) =3a(2) =15a(3) =73a(4) =387a(5) =2106a(6) =11998a(7) =69999a(8) =418104a(9) =2540368a(10) =15660843a(11) =97692822a(12) =615559931a(13) =3911866377a(14) =25044058215a(15) =161369414590