|
70 (seventy) is the natural number following 69 and preceding 71. ==In mathematics== Its factorization makes it a sphenic number. 70 is a Pell number and a generalized heptagonal number, one of only two numbers to be both.〔.〕 Also, it is the seventh pentagonal number and the fourth triskaidecagonal number, as well as the fifth pentatope number. The sum of the first twenty four squares starting from one is seventy squared. This relates seventy to the Leech lattice and thus string theory. It is the smallest Weird Number; a natural number that is abundant but not Semiperfect. Since it is possible to find sequences of 70 consecutive integers such that each inner member shares a factor with either the first or the last member, 70 is an Erdős–Woods number. In base 10, it is a Harshad number. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「70 (number)」の詳細全文を読む スポンサード リンク
|