a(n) = binomial(n, d(n)), where d(n) = A000005(n) is the number of divisors of n.

Terms

a(0) =1a(1) =1a(2) =3a(3) =4a(4) =10a(5) =15a(6) =21a(7) =70a(8) =84a(9) =210a(10) =55a(11) =924a(12) =78a(13) =1001a(14) =1365a(15) =4368a(16) =136a(17) =18564a(18) =171a(19) =38760a(20) =5985a(21) =7315a(22) =253a(23) =735471a(24) =2300a(25) =14950a(26) =17550a(27) =376740a(28) =406a(29) =5852925