Alternating partial sums of A000217.

Terms

a(0) =0a(1) =-1a(2) =2a(3) =-4a(4) =6a(5) =-9a(6) =12a(7) =-16a(8) =20a(9) =-25a(10) =30a(11) =-36a(12) =42a(13) =-49a(14) =56a(15) =-64a(16) =72a(17) =-81a(18) =90a(19) =-100a(20) =110a(21) =-121a(22) =132a(23) =-144a(24) =156a(25) =-169a(26) =182a(27) =-196a(28) =210a(29) =-225