a(n) is the sum of the elements on the antidiagonal of the difference table of the divisors of n.

Terms

a(0) =1a(1) =3a(2) =5a(3) =7a(4) =9a(5) =13a(6) =13a(7) =15a(8) =19a(9) =17a(10) =21a(11) =28a(12) =25a(13) =21a(14) =41a(15) =31a(16) =33a(17) =59a(18) =37a(19) =21a(20) =53a(21) =29a(22) =45a(23) =39a(24) =61a(25) =33a(26) =65a(27) =49a(28) =57a(29) =171