Number of separable type set partitions of {1..n}.

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =10a(5) =46a(6) =166a(7) =827a(8) =3795a(9) =20645a(10) =112124a(11) =672673a(12) =4163743a(13) =27565188a(14) =190168577a(15) =1381763398a(16) =10468226150a(17) =82844940414a(18) =681863474058