a(n) = n^n - n(n-1)/2.

A080523

a(n) = n^n - n(n-1)/2.

Terms

    a(0) =1a(1) =3a(2) =24a(3) =250a(4) =3115a(5) =46641a(6) =823522a(7) =16777188a(8) =387420453a(9) =9999999955a(10) =285311670556

External references