Triangle read by rows: number of set partitions of n elements with k circular connectors.

Terms

a(0) =1a(1) =1a(2) =0a(3) =1a(4) =0a(5) =1a(6) =1a(7) =0a(8) =3a(9) =1a(10) =1a(11) =0a(12) =8a(13) =4a(14) =2a(15) =1a(16) =1a(17) =20a(18) =15a(19) =14a(20) =1a(21) =1a(22) =6a(23) =53a(24) =61a(25) =68a(26) =11a(27) =3a(28) =1a(29) =25