awk 'BEGIN { for (i = 2; i <= 19; i++) -v i="$i" '{print $2 $i}'file2.txt > filei.txt}'

awk: BEGIN { for (i = 3; i <= 18; i++) -v i="$i" {print
awk:                                       ^ syntax error
awk: Commnadline:1: BEGIN { for (i = 3; i <= 18; i++) -v i="$i" {print
awk:  unexpected newline or end of string