A192374(n)/2.

Terms

a(0) =0a(1) =1a(2) =2a(3) =14a(4) =42a(5) =203a(6) =724a(7) =3100a(8) =11844a(9) =48517a(10) =190358a(11) =766922a(12) =3039726a(13) =12169871a(14) =48422248a(15) =193402552a(16) =770650824a(17) =3075264841a(18) =12260822378a(19) =48909765254a(20) =195040307826a(21) =777935950355