Hemiperfect数
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。
最小的k-hemiperfect数
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：
- 1 + 2 + 3 + 4 + 6 + 8 + 12 + 24 = 60 = 5/2 × 24.
参考资料
- ^ 1.0 1.1 Number Theory. Numericana.com. [2012-08-21]. （原始内容存档于2017-05-17）.
外部链接
整数数列线上大全（OEIS）中有包括以下k较小的k-hemiperfect数
- 5-hemiperfect数：A141643
- 7-hemiperfect数：A055153
- 9-hemiperfect数：A141645
- 11-hemiperfect数：A159271
- 13-hemiperfect数：A160678
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