a(n) = Sum_{k=0..n} binomial(k+5,5) * binomial(2*k,2*n-2*k).

Terms

a(0) =1a(1) =6a(2) =27a(3) =182a(4) =987a(5) =4620a(6) =20678a(7) =87732a(8) =355095a(9) =1387462a(10) =5258967a(11) =19416222a(12) =70086803a(13) =248046540a(14) =862694058a(15) =2954279732a(16) =9977518122a(17) =33278815920a(18) =109749059308a(19) =358231786128