A059460 Iteration of unitary-sigma function: a(n)=usigma(a(n-1)).

2, 3, 4, 5, 6, 12, 20, 30, 72, 90, 180, 300, 520, 756, 1120, 1584, 2040, 3888, 4148, 5580, 9600, 13416, 22176, 31680, 46800, 61880, 108864, 126880, 171864, 276480, 344232, 492480, 639600, 1039584, 1663200, 2306304, 3454080, 6390144