Terminal command equivalent of PHP implode when combining lines

Question

I have a couple of lines and want to group the line into 5 and then implode it for MySQL IN () query.

I have made it out until this

awk          


        

Answer 1

seq 16 |awk '{printf NR%5 ? (NR % 5 ==1 ? $0 : ","$0) : ","$0"\n";}'
#output:
1,2,3,4,5
6,7,8,9,10
11,12,13,14,15
16