jeneshicc https://blog.hatena.ne.jp/jeneshicc/ 落書き、時々落学 https://jeneshicc.hatenadiary.org/ Haskell 4n+1型の素数を平方数の和に分解する。 e.g. 5 = 1+4=1^2+4^2 1249 = 15^2+32^2 17669 = 70^2+113^2 225221 = 410^2+239^2 import Number import Data.List pRoot p = g.foldl1' f $ [1..div (p-1) 2] where f a b = mod (a*b) p g x = min x $ p-x sqSum p = let r = pRoot p in fst.until((==1).snd) next$ ((1,r),div (r*r+1) p) next ((… 190 <iframe src="https://hatenablog-parts.com/embed?url=https%3A%2F%2Fjeneshicc.hatenadiary.org%2Fentry%2F20081221%2F1229835537" title="4n+1素数の平方和分解 - 落書き、時々落学" class="embed-card embed-blogcard" scrolling="no" frameborder="0" style="display: block; width: 100%; height: 190px; max-width: 500px; margin: 10px 0px;"></iframe> Hatena Blog https://hatena.blog 2008-12-21 13:58:57 rich https://jeneshicc.hatenadiary.org/entry/20081221/1229835537 1.0 100%