a(n) = Sum_{k=0..2*n} binomial(2*n, k)^4.A249332a(n) = Sum_{k=0..2*n} binomial(2*n, k)^4.Terms a(0) =1a(1) =18a(2) =1810a(3) =263844a(4) =44916498a(5) =8345319268External referencesoeis: A249332