What for N=10 answer 4???

a1 = 1
a2 = 1
a3 = 2
a4 = 1
a5 = 3
a6 = 2
a7 = 3
a8 = 1
a9 = 4
a10 = 3

Maximal numbler among a1,...,a10 is a9, which is equal to 4.

I understand!Thank you!=)