Superparticular number

(n + 1)/n = 1 + 1/n

http://en.wikipedia.org/wiki/Superparticular_number

These ratios are also important in visual harmony. Most flags of the world's countries have a ratio of 3:2 between their length and height

Here are examples of flags with ratios other than 3:2

Ratio 1:1 Vatican City

http://flagspot.net/flags/va.html

Check the other ratios at

http://flagspot.net/flags/xf-size.html#1