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: The Euler -function : Arithmetic Function 玡: Multiplicative Arithmetic Functions

タ计计のタ计㎝

иノ multiplicative arithmetic function 阀├е―タ俱计ㄤタ计ぇ计のタ计㎝.

倒﹚タ俱计 n,  v(n) ボ n タ计计. 琂礛癸ヴ種 n $ \in$ $ \mathbb {N}$, v(n) 常Τ, ┮и盢ㄤΘ琌ㄧ计 v : $ \mathbb {N}$$ \to$$ \mathbb {N}$. 眖ㄧ计àㄓ, v 碞琌 arithmetic function. 倒﹚ n $ \in$ $ \mathbb {N}$ ― v(n) ㎡? 钡猭碞琌盢 n タ计礛计Τぶ. ㄒ 6 タ计Τ 1, 2, 3, 6, ┮ v(6) = 4. 硂妓―猭ノΑボ㎡? и到ノ summation $ \sum$ 才腹, 盢 v(n) 糶Θ

v(n) = $\displaystyle \sum_{d\vert n,d>0}^{}$1.

Α種碞琌–Ω d 骸ì d| nd > 0 碞Ω, ┮礛眔 n タ计计.

Proposition 2.2.1   癸ヴ種 n $ \in$ $ \mathbb {N}$,  v(n) ボ n タ计计. 玥 v : $ \mathbb {N}$$ \to$$ \mathbb {N}$ 琌 multiplicative arithmetic function. τ璝 n = p1n1 ... prnr, ㄤい pi 钵借计, 玥 v(n) = (n1 + 1) ... (nr + 1).

谍 . 璝 l : $ \mathbb {N}$$ \to$$ \mathbb {N}$ 琌 arithmetic function 骸ì癸ヴ種 n $ \in$ $ \mathbb {N}$, l(n) = 1, 玥 v(n) 

v(n) = $\displaystyle \sum_{d\vert n,d>0}^{}$l(d ).

パ癸ヴ種 a, b $ \in$ $ \mathbb {N}$, l(ab) = l(a)l(b) = 1, и l  (completely) multiplicative. パ Theorem 2.1.5v  multiplicative.

琂礛 v 琌 multiplicative, иノ Proposition 2.1.3 ―癸ヴ種 n $ \in$ $ \mathbb {N}$, v(n) ぇ. 碞琌弧и璶贝癚癸ヴ種借计 p のタ俱计 t, v(pt) ぇ. パ pt タ计碞琌 pi, ㄤい i $ \in$ {0, 1,..., t}, и眔 v(pt) = t + 1. 癸ヴ種 n $ \in$ $ \mathbb {N}$, 璝 n = 1, и v(n) = v(1) = 1; τ璝 n = p1n1 ... prnr ㄤい pi 钵借计, 玥パ v 琌 multiplicative 

v(n) = v(p1n1) ... v(prnr) = (n1 + 1) ... (nr + 1).

$ \qedsymbol$

羭ㄒㄓ弧, и璶― 360 タ计计, パ 360 = 23 . 32 . 5, ノ Proposition 2.2.1, ие碞眔 v(360) = (3 + 1)(2 + 1)(1 + 1) = 24. 眖硂柑產莱砰穦 multiplicative arithmetic function 矪. ┪砛― v(n) そΑ產蔼い厩逼舱碞ノ猭瞶眔筁. ノ猭瞶ㄤ龟碞㎝ v 琌 multiplicative 闽.

钡ㄓи贝癚タ计㎝. 倒﹚タ俱计 n,  $ \sigma$(n) ボ n ┮Τタ计ぇ㎝. 琂礛癸ヴ種 n $ \in$ $ \mathbb {N}$, $ \sigma$(n) 常Τ, ┮и盢ㄤΘ琌ㄧ计 $ \sigma$ : $ \mathbb {N}$$ \to$$ \mathbb {N}$. 眖ㄧ计àㄓ, $ \sigma$ 碞琌 arithmetic function. 倒﹚ n $ \in$ $ \mathbb {N}$ ― $ \sigma$(n) ㎡? 钡猭碞琌盢 n タ计礛场癬ㄓ. ㄒ 6 タ计Τ 1, 2, 3, 6, ┮ $ \sigma$(6) = 1 + 2 + 3 + 6 = 12. 硂妓―猭ノΑボ㎡? иΩ到ノ summation $ \sum$ 才腹, 盢 $ \sigma$(n) 糶Θ

$\displaystyle \sigma$(n) = $\displaystyle \sum_{d\vert n,d>0}^{}$d.

Α種碞琌–Ω d 骸ì d| nd > 0 碞 d, ┮礛眔 n タ计㎝.

Proposition 2.2.2   癸ヴ種 n $ \in$ $ \mathbb {N}$,  $ \sigma$(n) ボ n タ计计. 玥 $ \sigma$ : $ \mathbb {N}$$ \to$$ \mathbb {N}$ 琌 multiplicative arithmetic function. τ璝 n = p1n1 ... prnr, ㄤい pi 钵借计, 玥

$\displaystyle \sigma$(n) = $\displaystyle {\frac{p_1^{n_1+1}-1}{p_1-1}}$ ... $\displaystyle {\frac{p_r^{n_r+1}-1}{p_r-1}}$.

谍 . 璝 $ \mathcal {I}$ : $ \mathbb {N}$$ \to$$ \mathbb {N}$ 琌 arithmetic function 骸ì癸ヴ種 n $ \in$ $ \mathbb {N}$, $ \mathcal {I}$(n) = n, 玥 $ \sigma$(n) 

$\displaystyle \sigma$(n) = $\displaystyle \sum_{d\vert n,d>0}^{}$$\displaystyle \mathcal {I}$(d ).

パ癸ヴ種 a, b $ \in$ $ \mathbb {N}$, $ \mathcal {I}$(ab) = ab = $ \mathcal {I}$(a)$ \mathcal {I}$(b), и $ \mathcal {I}$  (completely) multiplicative. パ Theorem 2.1.5$ \sigma$  multiplicative.

琂礛 $ \sigma$ 琌 multiplicative, иノ Proposition 2.1.3 ―癸ヴ種 n $ \in$ $ \mathbb {N}$, $ \sigma$(n) ぇ. 碞琌弧и璶贝癚癸ヴ種借计 p のタ俱计 t, $ \sigma$(pt) ぇ. パ pt タ计碞琌 pi, ㄤい i $ \in$ {0, 1,..., t}, и眔 $ \sigma$(pt) = 1 + p + ... + pt. パ 1, p,..., pt 琌そゑ p 单ゑ计, и眔

$\displaystyle \sigma$(pt) = $\displaystyle {\frac{p^{t+1}-1}{p-1}}$.

癸ヴ種 n $ \in$ $ \mathbb {N}$, 璝 n = 1, и $ \sigma$(n) = $ \sigma$(1) = 1; τ璝 n = p1n1 ... prnr ㄤい pi 钵借计, 玥パ $ \sigma$ 琌 multiplicative 

$\displaystyle \sigma$(n) = $\displaystyle \sigma$(p1n1) ... $\displaystyle \sigma$(prnr) = $\displaystyle {\frac{p_1^{n_1+1}-1}{p_1-1}}$ ... $\displaystyle {\frac{p_r^{n_r+1}-1}{p_r-1}}$.

$ \qedsymbol$

羭ㄒㄓ弧, и璶― 360 タ计㎝, パ 360 = 23 . 32 . 5, ノ Proposition 2.2.2, ие碞眔

$\displaystyle \sigma$(360) = $\displaystyle {\frac{2^4-1}{2-1}}$$\displaystyle {\frac{3^3-1}{3-1}}$$\displaystyle {\frac{5^2-1}{5-1}}$ = 15 . 13 . 6 = 1170.


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: The Euler -function : Arithmetic Function 玡: Multiplicative Arithmetic Functions
Li 2007-06-28