Number of 2-dimensional directed compact animals of size n.

Terms

a(0) =1a(1) =2a(2) =5a(3) =13a(4) =34a(5) =90a(6) =239a(7) =635a(8) =1689a(9) =4494a(10) =11960a(11) =31832a(12) =84727a(13) =225524a(14) =600302a(15) =1597904a(16) =4253371a(17) =11321838a(18) =30137079a(19) =80220557a(20) =213535632a(21) =568401380a(22) =1513003529