a(0) = 0; a(n) = a(n-1) - n^2 if positive and new, otherwise a(n) = a(n-1) + n^2.

Terms

a(0) =0a(1) =1a(2) =5a(3) =14a(4) =30a(5) =55a(6) =19a(7) =68a(8) =4a(9) =85a(10) =185a(11) =64a(12) =208a(13) =39a(14) =235a(15) =10a(16) =266a(17) =555a(18) =231a(19) =592a(20) =192a(21) =633a(22) =149a(23) =678a(24) =102a(25) =727a(26) =51a(27) =780a(28) =1564a(29) =723