a(n) = (n^n + n^2)/2.A214647a(n) = (n^n + n^2)/2.Terms a(0) =1a(1) =4a(2) =18a(3) =136a(4) =1575a(5) =23346a(6) =411796a(7) =8388640a(8) =193710285a(9) =5000000050a(10) =142655835366External referencesoeis: A214647