Denominator of Sum_{k=1..n} phi(k)/k^2.

Terms

a(0) =1a(1) =4a(2) =36a(3) =72a(4) =1800a(5) =1800a(6) =88200a(7) =176400a(8) =529200a(9) =105840a(10) =12806640a(11) =12806640a(12) =2164322160a(13) =2164322160a(14) =10821610800a(15) =21643221600