a(n) = smallest number k such that sigma(k+n) - sigma(k) = k + n, or -1 if no solution exists.

Terms

a(0) =1a(1) =1a(2) =7a(3) =1a(4) =3577a(5) =1a(6) =25a(7) =8a(8) =13a(9) =1a(10) =403668223a(11) =1a(12) =833a(13) =262a(14) =19a(15) =1a(16) =27a(17) =1a(18) =793a(19) =5a(20) =45a(21) =1a(22) =1795a(23) =66a(24) =8a(25) =9a(26) =31a(27) =1a(28) =2005a(29) =1