Number of set partitions of [n] such that for each block b the smallest integer interval containing b has at most four elements and for at least one block c the smallest integer interval containing c has exactly four elements.

A320554

Number of set partitions of [n] such that for each block b the smallest integer interval containing b has at most four elements and for at least one block c the smallest integer interval containing c has exactly four elements.

Terms

    a(0) =5a(1) =17a(2) =45a(3) =121a(4) =336a(5) =901a(6) =2347a(7) =6014a(8) =15314a(9) =38766a(10) =97531a(11) =244054a(12) =608339a(13) =1511919a(14) =3748379a(15) =9273353a(16) =22901665a(17) =56477538a(18) =139114445a(19) =342325451a(20) =841676972a(21) =2067997764a(22) =5078117000a(23) =12463618356a(24) =30577931115a(25) =74993361731a(26) =183870516407a(27) =450708620604

External references