Displaying similar documents to “On the number of perfect binary quadratic forms.”

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.

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.

Cyclotomic quadratic forms

François Sigrist (2000)

Journal de théorie des nombres de Bordeaux

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Voronoï ’s algorithm is a method for obtaining the complete list of perfect n -dimensional quadratic forms. Its generalization to G -forms has the advantage of running in a lower-dimensional space, and furnishes a finite, and complete, classification of G -perfect forms ( G is a finite subgroup of G L ( n , ℤ ) ) . We study the standard, φ ( m ) -dimensional irreducible representation of the cyclic group C m of order m , and give the, often new, densest G -forms. Perfect cyclotomic forms are completely classified...

A basic approach to the perfect extensions of spaces

Giorgio Nordo (1997)

Commentationes Mathematicae Universitatis Carolinae

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In this paper we generalize the notion of of a Tychonoff space to a generic extension of any space by introducing the concept of . This allow us to simplify the treatment in a basic way and in a more general setting. Some [S 1 ], [S 2 ], and [D]’s results are improved and new characterizations for perfect (Hausdorff) extensions of spaces are obtained.

On a sum of divisors problem.

De Koninck, Jean-Marie, Ivić, Aleksandar (1998)

Publications de l'Institut Mathématique. Nouvelle Série

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