For any m∈N*, the number of terms in the sequence {an} which is not more than 72m is denoted as bm, and the sum of the first m terms in the sequence {bm} and Sm is found.

M = 1, and the number of items in {an} not more than 72* 1=72 is expressed as b 1.

M = 2, and the number of items in {an} not exceeding 72*2= 144 is denoted as b2.

......

In this way, we get the sequence {bm}