Number of permutations in S_n avoiding 31{bar 5}{bar 4}2 (i.e., every occurrence of 312 is contained in an occurrence of a 31542).

A137550

Number of permutations in S_n avoiding 31{bar 5}{bar 4}2 (i.e., every occurrence of 312 is contained in an occurrence of a 31542).

Terms

    a(0) =1a(1) =1a(2) =2a(3) =5a(4) =14a(5) =43a(6) =144a(7) =522a(8) =2030a(9) =8398a(10) =36714a(11) =168793a(12) =813112a(13) =4091735a(14) =21451972a(15) =116891160a(16) =660554822a(17) =3863775322a(18) =23353384298a(19) =145634065581a(20) =935743895590

External references