Number of identity trees with 3-colored nodes.

Terms

a(0) =1a(1) =3a(2) =3a(3) =9a(4) =39a(5) =189a(6) =981a(7) =5490a(8) =31674a(9) =189954a(10) =1170126a(11) =7382745a(12) =47494197a(13) =310712808a(14) =2061987642a(15) =13855192866a(16) =94113385437a(17) =645424668666