Number of ternary Lyndon words with exactly four 1's.

Terms

a(0) =2a(1) =9a(2) =40a(3) =137a(4) =448a(5) =1336a(6) =3840a(7) =10540a(8) =28160a(9) =73168a(10) =186368a(11) =465808a(12) =1146880a(13) =2785024a(14) =6684672a(15) =15875520a(16) =37355520a(17) =87161600a(18) =201850880a(19) =464254208a(20) =1061158912a(21) =2411718656a(22) =5452595200a(23) =12268325888a(24) =27481079808a(25) =61303918592