Number of maximal self-avoiding walks from NW to SW corners of a 4-by-n grid.

Terms

a(0) =1a(1) =1a(2) =4a(3) =8a(4) =23a(5) =55a(6) =144a(7) =360a(8) =921a(9) =2329a(10) =5924a(11) =15024a(12) =38159a(13) =96847a(14) =245888a(15) =624176a(16) =1584593a(17) =4022609a(18) =10211940a(19) =25924088a(20) =65811431a(21) =167069767a(22) =424126160a(23) =1076693080a(24) =2733310377a(25) =6938824361a(26) =17615009476a(27) =44717740000a(28) =113521160607a(29) =288186606623