Total number of edges in all trees on n nodes.

Terms

a(0) =0a(1) =1a(2) =2a(3) =6a(4) =12a(5) =30a(6) =66a(7) =161a(8) =376a(9) =954a(10) =2350a(11) =6061a(12) =15612a(13) =41067a(14) =108374a(15) =289800a(16) =778064a(17) =2105739a(18) =5723190a(19) =15638235a(20) =42890100a(21) =118098876a(22) =326217628a(23) =903897631a(24) =2511285360a(25) =6994836250a(26) =19527701960a(27) =54632961864a(28) =153147864380a(29) =430095282258