Truncated square pyramid numbers: a(n) = Sum_{k = n..2*n} k^2.

Terms

a(0) =0a(1) =5a(2) =29a(3) =86a(4) =190a(5) =355a(6) =595a(7) =924a(8) =1356a(9) =1905a(10) =2585a(11) =3410a(12) =4394a(13) =5551a(14) =6895a(15) =8440a(16) =10200a(17) =12189a(18) =14421a(19) =16910a(20) =19670a(21) =22715a(22) =26059a(23) =29716a(24) =33700a(25) =38025a(26) =42705a(27) =47754a(28) =53186a(29) =59015