Number of walks on square lattice.

Terms

a(0) =20a(1) =75a(2) =189a(3) =392a(4) =720a(5) =1215a(6) =1925a(7) =2904a(8) =4212a(9) =5915a(10) =8085a(11) =10800a(12) =14144a(13) =18207a(14) =23085a(15) =28880a(16) =35700a(17) =43659a(18) =52877a(19) =63480a(20) =75600a(21) =89375a(22) =104949a(23) =122472a(24) =142100a(25) =163995a(26) =188325a(27) =215264a(28) =244992a(29) =277695