Number of n-step closed walks on kagome lattice.

Terms

a(0) =1a(1) =0a(2) =4a(3) =4a(4) =28a(5) =60a(6) =264a(7) =784a(8) =3004a(9) =10204a(10) =37824a(11) =135784a(12) =502784a(13) =1851200a(14) =6901696a(15) =25766144a(16) =96797244a(17) =364655100a(18) =1379120400a(19) =5230011896a(20) =19890313128a(21) =75823622984a(22) =289698620336