a(n) = (23^n - 1)/22.A218726a(n) = (23^n - 1)/22.Terms a(0) =0a(1) =1a(2) =24a(3) =553a(4) =12720a(5) =292561a(6) =6728904a(7) =154764793a(8) =3559590240a(9) =81870575521External referencesoeis: A218726