Number of permutations on n letters without double falls and without initial falls.

A080635

Number of permutations on n letters without double falls and without initial falls.

Terms

    a(0) =1a(1) =1a(2) =1a(3) =3a(4) =9a(5) =39a(6) =189a(7) =1107a(8) =7281a(9) =54351a(10) =448821a(11) =4085883a(12) =40533129a(13) =435847959a(14) =5045745069a(15) =62594829027a(16) =828229153761

External references