Number of compact-rooted directed animals of size n having 3 source points.

Terms

a(0) =1a(1) =4a(2) =14a(3) =45a(4) =140a(5) =427a(6) =1288a(7) =3858a(8) =11505a(9) =34210a(10) =101530a(11) =300950a(12) =891345a(13) =2638650a(14) =7809000a(15) =23107488a(16) =68375547a(17) =202336092a(18) =598817490a(19) =1772479905a(20) =5247421410a(21) =15538054455a(22) =46019183840a(23) =136325212750a(24) =403933918375