Number of set partitions of [n] such that j is member of block b only if b = 1 or at least one of j-1, ..., j-3 is member of a block >= b-1.

A287666

Number of set partitions of [n] such that j is member of block b only if b = 1 or at least one of j-1, ..., j-3 is member of a block >= b-1.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =52a(6) =202a(7) =861a(8) =3970a(9) =19596a(10) =102703a(11) =567867a(12) =3295439a(13) =19986462a(14) =126231946a(15) =827759525a(16) =5621051650a(17) =39439867696a(18) =285368007479

External references