{"categories":["Scala"],"url":"https://inamori.hateblo.jp/entry/20110822/p1","provider_name":"Hatena Blog","author_url":"https://blog.hatena.ne.jp/inamori/","published":"2011-08-22 00:00:00","type":"rich","width":"100%","author_name":"inamori","title":"Scala\u3067Project Euler\uff0874\uff09","blog_title":"inamori\u2019s diary","description":"Problem 44\u3069\u3046\u3059\u308c\u3070\u3046\u307e\u304f\u89e3\u3051\u308b\u3093\u3067\u3057\u3087\u3046\u306d\u3002 D = Pk - Pj = Pi \u3068\u3057\u3066\u3001 k(3k - 1) / 2 - j(3j - 1) / 2 = i(3i - 1) / 2 (36k2 - 12k) - (36j2 - 12j) = (36i2 - 12j) (6k - 1)2 - (6j - 1)2 = (6i - 1)2 - 1 \u3053\u3053\u3067\u3001 a = 6i - 1 b = 6j - 1 c = 6k - 1 \u3068\u7f6e\u304f\u3068\u3001 c2 - b2 = a2 - 1 (c - b)(c + b) = (a - 1)(a + 1) \u7a4d\u306e\u5f62\u306b\u6301\u3061\u8fbc\u3093\u3060\u3089\u7d20\u56e0\u6570\u5206\u89e3\u3067\u3059\u3002(a - 1)(a +\u2026","blog_url":"https://inamori.hateblo.jp/","image_url":null,"height":"190","version":"1.0","html":"<iframe src=\"https://hatenablog-parts.com/embed?url=https%3A%2F%2Finamori.hateblo.jp%2Fentry%2F20110822%2Fp1\" title=\"Scala\u3067Project Euler\uff0874\uff09 - inamori\u2019s diary\" class=\"embed-card embed-blogcard\" scrolling=\"no\" frameborder=\"0\" style=\"display: block; width: 100%; height: 190px; max-width: 500px; margin: 10px 0px;\"></iframe>","provider_url":"https://hatena.blog"}