a(n) = Sum_{k=0..floor(n/2)} |Stirling1(n - k, k)|.

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =3a(5) =9a(6) =36a(7) =176a(8) =1030a(9) =7039a(10) =55098a(11) =486346a(12) =4780445a(13) =51787405a(14) =613045468a(15) =7873065045a(16) =109021348618