a(n) = Sum_{m=1..n-1} floor(m(n-2)/2)^2.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =14a(5) =62a(6) =220a(7) =547a(8) =1260a(9) =2444a(10) =4560a(11) =7685a(12) =12650a(13) =19466a(14) =29484a(15) =42567a(16) =60760a(17) =83672a(18) =114240a(19) =151689a(20) =200070a(21) =258070a(22) =331100a(23) =417131a(24) =523204a(25) =646372a(26) =795600a(27) =966797a(28) =1171170a(29) =1403234