Number of derangements of [n] avoiding the patterns 123, 132 and 213.

Terms

a(0) =0a(1) =1a(2) =2a(3) =4a(4) =4a(5) =9a(6) =12a(7) =25a(8) =30a(9) =64a(10) =80a(11) =169a(12) =208a(13) =441a(14) =546a(15) =1156a(16) =1428a(17) =3025a(18) =3740a(19) =7921a(20) =9790a(21) =20736a(22) =25632a(23) =54289a(24) =67104a(25) =142129a(26) =175682a(27) =372100a(28) =459940a(29) =974169