a(n) = A027170(2n, n).

Terms

a(0) =1a(1) =10a(2) =42a(3) =156a(4) =570a(5) =2096a(6) =7784a(7) =29168a(8) =110106a(9) =418128a(10) =1595616a(11) =6113740a(12) =23505352a(13) =90633796a(14) =350351636a(15) =1357278296a(16) =5268292826a(17) =20483876816a(18) =79765662896a(19) =311038321436