Clausen numbers based on the strictly proper divisors of n, 1 < d < n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =3a(5) =1a(6) =3a(7) =1a(8) =15a(9) =1a(10) =3a(11) =1a(12) =105a(13) =1a(14) =3a(15) =1a(16) =15a(17) =1a(18) =21a(19) =1a(20) =165a(21) =1a(22) =3a(23) =1a(24) =1365a(25) =1a(26) =3a(27) =1a(28) =15a(29) =1