This one-liner will list packages that were explicitly installed by user.

yum-installed

#/bin/sh

# Description: Lists packages that were explicitly installed by user.
# Run this:    curl -Ls goo.gl/RV7oiB | sh

export LC_ALL=C

MIN=2  # First is the OS installation
MAX=$(yum history | awk 'NR==4 { print $1 }')

yum history info $MIN..$MAX \
| grep '\sInstall\s' \
| awk '{ print $2 }' \
| awk '{ sub(/\-[^\-]+\-[^\-]+$/, ""); print }' \
| awk 'BEGIN { printf("\nyum install ") } { printf("%s ", $0) } END { printf "\n" }' \
| awk 'BEGIN { printf("To install packages installed on this machine, enter this command:") } { print $0 }'