Euclid discovered that the first four perfect numbers are generated by the formula 2n−1(2n − 1):
for n = 2: 21(22 − 1) = 6
for n = 3: 22(23 − 1) = 28
for n = 5: 24(25 − 1) = 496
for n = 7: 26(27 − 1) = 8128
No room for 68, 69, 5, 85 or any other number that
I've recently had.