Displaying similar documents to “Products of conjugacy classes in perfect linear groups. Extended covering number.”

W-perfect groups

Selami Ercan (2015)

Open Mathematics

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In the present article we define W-paths of elements in a W-perfect group as a useful tools and obtain their basic properties.

On near-perfect and deficient-perfect numbers

Min Tang, Xiao-Zhi Ren, Meng Li (2013)

Colloquium Mathematicae

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For a positive integer n, let σ(n) denote the sum of the positive divisors of n. Let d be a proper divisor of n. We call n a near-perfect number if σ(n) = 2n + d, and a deficient-perfect number if σ(n) = 2n - d. We show that there is no odd near-perfect number with three distinct prime divisors and determine all deficient-perfect numbers with at most two distinct prime factors.

Odd perfect numbers of a special form

Tomohiro Yamada (2005)

Colloquium Mathematicae

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We show that there is an effectively computable upper bound of odd perfect numbers whose Euler factors are powers of fixed exponent.