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-2 is member of a block >= b-1.
A275605
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-2 is member of a block >= b-1.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =51a(6) =191a(7) =773a(8) =3336a(9) =15207a(10) =72697a(11) =362447a(12) =1876392a(13) =10051083a(14) =55544661a(15) =315899245a(16) =1845139684a(17) =11048651523a(18) =67719859612a(19) =424287619507
External references
- oeis: A275605