a(n) = (1/2) * A027170(2n, n).

Terms

a(0) =5a(1) =21a(2) =78a(3) =285a(4) =1048a(5) =3892a(6) =14584a(7) =55053a(8) =209064a(9) =797808a(10) =3056870a(11) =11752676a(12) =45316898a(13) =175175818a(14) =678639148a(15) =2634146413a(16) =10241938408a(17) =39882831448a(18) =155519160718a(19) =607181138848