Number of rooted set partitions.

Terms

a(0) =0a(1) =1a(2) =2a(3) =6a(4) =20a(5) =75a(6) =312a(7) =1421a(8) =7016a(9) =37260a(10) =211470a(11) =1275725a(12) =8142840a(13) =54776761a(14) =387022118a(15) =2863489830a(16) =22127336720a(17) =178162416499