a(n) = Sum_{k=0..n} (k!)^n * binomial(n,k).A343928a(n) = Sum_{k=0..n} (k!)^n * binomial(n,k).Terms a(0) =1a(1) =2a(2) =7a(3) =244a(4) =337061a(5) =24923091206External referencesoeis: A343928