Number of set partitions of [n] such that at least one of the block sizes is 2.

A327885

Number of set partitions of [n] such that at least one of the block sizes is 2.

Terms

    a(0) =0a(1) =0a(2) =1a(3) =3a(4) =9a(5) =35a(6) =150a(7) =672a(8) =3269a(9) =17271a(10) =97155a(11) =578985a(12) =3654750a(13) =24331320a(14) =170074177a(15) =1244911605a(16) =9520843575a(17) =75890001665a(18) =629104453236

External references