a(n) is the number of permutations of [n] which avoid the patterns 1234, 1324, and 2413.

A369626

a(n) is the number of permutations of [n] which avoid the patterns 1234, 1324, and 2413.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =75a(6) =265a(7) =925a(8) =3201a(9) =11017a(10) =37793a(11) =129393a(12) =442497a(13) =1512225a(14) =5165953a(15) =17643457a(16) =60250113a(17) =205729921a(18) =702452225a(19) =2398414593a(20) =8188884993

External references