3rd power of rooted tree enumerator; number of linear forests of 3 rooted trees.

Terms

a(0) =1a(1) =3a(2) =9a(3) =25a(4) =69a(5) =186a(6) =503a(7) =1353a(8) =3651a(9) =9865a(10) =26748a(11) =72729a(12) =198447a(13) =543159a(14) =1491402a(15) =4107152a(16) =11342826a(17) =31408719a(18) =87189987a(19) =242603970a(20) =676524372a(21) =1890436117a(22) =5292722721a(23) =14845095153a(24) =41708679697a(25) =117372283086a(26) =330795842217