a(n) is the permanent of the Vandermonde matrix of the divisors of n.

Terms

a(0) =1a(1) =3a(2) =4a(3) =74a(4) =6a(5) =16272a(6) =8a(7) =57520a(8) =426a(9) =158680a(10) =12a(12) =14a(13) =764848a(14) =729720a(15) =5715121152a(16) =18a(18) =20a(20) =3386712a(21) =6680080a(22) =24a(24) =4430a(25) =15040792a(26) =10986840a(28) =30