a(n) = A064837(n)/2.

Terms

a(0) =0a(1) =1a(2) =9a(3) =57a(4) =210a(5) =585a(6) =1355a(7) =2769a(8) =5156a(9) =8945a(10) =14669a(11) =22985a(12) =34678a(13) =50681a(14) =72079a(15) =100129a(16) =136264a(17) =182113a(18) =239505a(19) =310489a(20) =397338a(21) =502569a(22) =628947a(23) =779505a(24) =957548a(25) =1166673a(26) =1410773a(27) =1694057a(28) =2021054a(29) =2396633