Choose a number of numbers from 1, 2, 3, ..., 7 such that the sum of the even numbers is equal to the sum of the odd numbers. Then how many ways to meet the conditions.
从1、2、3、…、7中选择若干个数，使得其中偶数之和等于奇数之和．则符合条件的取法多少种．
<result>7</result>