a(n) = A192423(n)/2.

Terms

a(0) =1a(1) =0a(2) =2a(3) =1a(4) =8a(5) =10a(6) =39a(7) =70a(8) =208a(9) =439a(10) =1162a(11) =2640a(12) =6641a(13) =15600a(14) =38362a(15) =91481a(16) =222688a(17) =534650a(18) =1295559a(19) =3119990a(20) =7544888a(21) =18194639a(22) =43958642a(23) =106072320a(24) =256167361a(25) =618303360a(26) =1492941842a(27) =3603915601a(28) =8701212248a(29) =21005629450