a(n) = (n^n - n^2)/2.A214698a(n) = (n^n - n^2)/2.Terms a(0) =0a(1) =0a(2) =9a(3) =120a(4) =1550a(5) =23310a(6) =411747a(7) =8388576a(8) =193710204a(9) =4999999950a(10) =142655835245External referencesoeis: A214698