Odd abundant number
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An odd abundant number is an odd number that its sum-of divisors greater than the twice of itself.
Examples[edit]
- The first example is 945 (33× 5× 7). Its prime factors are 3, 5, and 7. The next following eleven odd abundant numbers are
1575, 2205, 2835, 3465, 4095, 4725, 5355, 5775, 5985, 6435, 6615.
- Odd abundant numbers below 500000 are in On-Line Encyclopedia of Integer Sequences A005231.
Formulas[edit]
The following formula
[1] presents 62 abundant numbers, but it fails if
.
The second formula
[2] presents 192 abundant numbers, but fails if
The third formula
fails if .
Properties[edit]
- A calculation was given by Iannucci shows how to find the smallest abundant number not divisible by the first n primes.
- An abundant number with abundance 1 is called a quasiperfect number, although none have yet been found. A quasiperfect number must be an odd square number having a value above 1030.
References[edit]
- ↑ "More Odd Abundant Sequences" (PDF). JAY. SCHIFFMAN. 2005. Archived from the original (PDF) on 2015-09-13. Retrieved 2017-01-2. Unknown parameter
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(help) - ↑ "More Odd Abundant Sequences" (PDF). JAY. SCHIFFMAN. 2005. Archived from the original (PDF) on 2015-09-13. Retrieved 2017-01-26. Unknown parameter
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ignored (help) - ↑ "More Odd Abundant Sequences" (PDF). JAY. SCHIFFMAN. 2005. Archived from the original (PDF) on 2015-09-13. Retrieved 2017-01-26. Unknown parameter
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