Code:
awk '{$1=$NF="";$0=substr($0,2,length($0)-2)} NR>4' OFS="," file
36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36,36
37,37,37,37,37,37,37,37,38,38,38,38,38,39,39,39,39,39,40,40,40,40,41,41,41,41,42,42
42,43,43,43,43,44,44,44,45,45,45,45,46,46,46,46,47,47,47,47,47,48,48,48,48,49,49,49,49,49,50