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来自维基百科,自由的百科全书
Hemiperfect数(hemiperfect number)是指一正整数的过剩指数为奇数除以2,过剩指数(abundancy index)就是除数函数(包括本身的所有正因数和)除以正整数后的结果。
下表列出在k ≤ 17范围内.各k值下k-hemiperfect数的最小值(OEIS数列A088912)。
k | 最小的k-hemiperfect数 |
---|---|
3 | 2(也是唯一的3-hemiperfect数) |
5 | 24 |
7 | 4320 |
9 | 8910720 |
11 | 17116004505600 |
13 | 170974031122008628879954060917200710847692800 |
15 | 12749472205565550032020636281352368036406720997031277595140988449695952806020854579200000[1] |
17 | 27172904004644864174776390325441204588387876949911859015099963347683477337589882757168182488651338324482275518065870009252589097916253652597707421065171952334010184222064839170719744000000000[1] |
例如24的除数函数为24的5/2倍.因此24为5-hemiperfect数:
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