a(n) = Sum_{k=0..n} (n^2)!/((n^2-n*k)!*k!^n).A306207a(n) = Sum_{k=0..n} (n^2)!/((n^2-n*k)!*k!^n).Terms a(0) =1a(1) =2a(2) =19a(3) =9745a(4) =768211081External referencesoeis: A306207