a(n) = (6/((4*n+1)*(4*n+2)))*binomial(5*n,n).

Terms

a(0) =3a(1) =1a(2) =3a(3) =15a(4) =95a(5) =690a(6) =5481a(7) =46376a(8) =411255a(9) =3781635a(10) =35791910a(11) =346821930a(12) =3427001253a(13) =34425730640a(14) =350732771160