I collect fancy serial number notes. One of the rarities I look for is whether a bill has a serial number with all even or odd numbers. Only 0.39% of 8-digit numbers have this property. I quit collecting the bills that do not contain all of the odd or all of the even numbers. The very odd part is I have found only seven bills with only the odd numbers and sixty-seven bills with only the even numbers. This big difference has me stumped.