Second differences of sigma(n).

Terms

a(0) =-1a(1) =2a(2) =-4a(3) =7a(4) =-10a(5) =11a(6) =-9a(7) =7a(8) =-11a(9) =22a(10) =-30a(11) =24a(12) =-10a(13) =7a(14) =-20a(15) =34a(16) =-40a(17) =41a(18) =-32a(19) =14a(20) =-16a(21) =48a(22) =-65a(23) =40a(24) =-13a(25) =18a(26) =-42a(27) =68a(28) =-82a(29) =71