gistfile1.txt

#!/bin/bash

multiples=()

is_mult () {
	local n=$1
	local m=$2
	if ! (( n % m )); then
		return 0
	else
		return 1
	fi
}

for n in {1..999}; do
	if is_mult "$n" 3 || is_mult "$n" 5; then
		multiples+=("$n")
	fi
done

IFS=+ sum="${multiples[*]}"

echo "$sum" | bc