Number of set partitions of {1, ..., n} that avoid enhanced 4-crossings (or enhanced 4-nestings).

A192855

Number of set partitions of {1, ..., n} that avoid enhanced 4-crossings (or enhanced 4-nestings).

Terms

    a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =52a(6) =203a(7) =876a(8) =4120a(9) =20883a(10) =113034a(11) =648410a(12) =3917021a(13) =24785452a(14) =163525976a(15) =1120523114a(16) =7947399981a(17) =58172358642a(18) =438300848329

External references