The first terms, alongside the corresponding sequences b_n, are:
n a(n) b_n
-- ---- ----------------------------------------------
1 1 [1, 1]
2 2 [2, 2, 1]
3 6 [6, 6, 3, 1]
4 6 [6, 6, 12, 4, 1]
5 30 [30, 30, 60, 20, 5, 1]
6 20 [20, 20, 40, 120, 30, 6, 1]
7 140 [140, 140, 280, 840, 210, 42, 7, 1]
8 70 [70, 70, 140, 420, 1680, 336, 56, 8, 1]
9 70 [70, 70, 35, 105, 420, 84, 504, 72, 9, 1]
10 7 [7, 7, 14, 42, 168, 840, 5040, 720, 90, 10, 1]
