Number of distinct 'failure tables' for a string of length n.

Terms

a(0) =1a(1) =2a(2) =4a(3) =9a(4) =20a(5) =47a(6) =110a(7) =263a(8) =630a(9) =1525a(10) =3701a(11) =9039a(12) =22140a(13) =54460a(14) =134339a(15) =332439a(16) =824735a(17) =2051307a(18) =5113298a(19) =12773067a(20) =31968041a(21) =80152901a(22) =201297338a(23) =506324357a(24) =1275385911a(25) =3216901194a(26) =8124150323a(27) =20541362001a(28) =51994801119a(29) =131747424892