Arises from enumeration of a certain class of partial knight's paths on the square grid.

Terms

a(0) =0a(1) =1a(2) =0a(3) =2a(4) =1a(5) =9a(6) =10a(7) =42a(8) =64a(9) =213a(10) =400a(11) =1180a(12) =2510a(13) =6918a(14) =15842a(15) =42134a(16) =100966a(17) =263894a(18) =650688a(19) =1687746a(20) =4238855a(21) =10968196a(22) =27888906a(23) =72187356a(24) =185141385a(25) =480025465a(26) =1238940890a(27) =3219591600a(28) =8350054339a(29) =21752631006