a(n) = Sum_{k=0..n} (k!)^k * binomial(n,k).A343899a(n) = Sum_{k=0..n} (k!)^k * binomial(n,k).Terms a(0) =1a(1) =2a(2) =7a(3) =232a(4) =332669a(5) =24884861086External referencesoeis: A343899