Alternating sum of squares to n.

Terms

a(0) =-1a(1) =3a(2) =-6a(3) =10a(4) =-15a(5) =21a(6) =-28a(7) =36a(8) =-45a(9) =55a(10) =-66a(11) =78a(12) =-91a(13) =105a(14) =-120a(15) =136a(16) =-153a(17) =171a(18) =-190a(19) =210a(20) =-231a(21) =253a(22) =-276a(23) =300a(24) =-325a(25) =351a(26) =-378a(27) =406a(28) =-435a(29) =465