a(n) = n*(1 + n^n)/2.A108398a(n) = n*(1 + n^n)/2.Terms a(0) =0a(1) =1a(2) =5a(3) =42a(4) =514a(5) =7815a(6) =139971a(7) =2882404a(8) =67108868a(9) =1743392205a(10) =50000000005External referencesoeis: A108398