Number of multi-directed animals on the triangular lattice.

Terms

a(0) =1a(1) =3a(2) =11a(3) =44a(4) =184a(5) =790a(6) =3450a(7) =15242a(8) =67895a(9) =304267a(10) =1369761a(11) =6188002a(12) =28031111a(13) =127253141a(14) =578694237a(15) =2635356807a(16) =12015117401a(17) =54831125131a(18) =250418753498