So in the 16th Century, Pope Gregory XIII tweak the system again so that leap ears would occur in any year that's divisible by four, but only in centuries that are evenly divided by 400, confusing, I know.
And all in all the ones that we care about, the subsets with a sum divisible by five, have been put over here on the left and it looks like there's a total of eight of them.
The whole massive uplift of the range is one great picture, not clearly divisible into smaller ones; differing much in this respect from the older, and what may be called, riper mountains of the Coast Range.
Eratosthenes of Cyrene was a 3rd century BCE mathematician from ancient Greece interested in prime numbers, that is numbers only divisible by 1 and themselves.
Cyrene 的埃拉托色尼 (Eratosthenes of Cyrene) 是公元前 3 纪来自古希腊的数学家,他对素数很感兴趣,素数只能被 1 和它们本身整除。