a(0) = a(1) = 1; a(n) = 5 * Sum_{k=0..n-2} a(k) * a(n-k-2).

Terms

a(0) =1a(1) =1a(2) =5a(3) =10a(4) =55a(5) =150a(6) =775a(7) =2550a(8) =12500a(9) =46250a(10) =219375a(11) =875000a(12) =4075000a(13) =17071250a(14) =78796875a(15) =341100000a(16) =1569350000a(17) =6947531250a(18) =31966000000a(19) =143761750000a(20) =662668906250