a(n) = Sum_{k=0..n} binomial(n^2, k^2).A206849a(n) = Sum_{k=0..n} binomial(n^2, k^2).Terms a(0) =1a(1) =2a(2) =6a(3) =137a(4) =13278a(5) =4098627a(6) =8002879629External referencesoeis: A206849