**Volume 24** ▶ Number 1 ▷ Number 2 ▷ Number 3

**On a class of quartic Diophantine equations of at least five variables**

*Original research paper. Pages 1—9*

Hamid Reza Abdolmalki and Farzali Izadi

Full paper (PDF, 179 Kb) | Abstract

**On negative Pell equations: Solvability and unsolvability in integers**

*Original research paper. Pages 10—26*

Hsin-Te Chiang, Mei-Ru Ciou, Chia-Ling Tsai, Yuh-JennWu and Chiun-Chang Lee

Full paper (PDF, 248 Kb) | Abstract

**Some new families of positive-rank elliptic curves arising from Pythagorean triples**

*Original research paper. Pages 27—36*

Mehdi Baghalaghdam and Farzali Izadi

Full paper (PDF, 193 Kb) | Abstract

**On the derivatives of bivariate Fibonacci polynomials**

*Original research paper. Pages 37—46*

Tuba Çakmak and Erdal Karaduman

Full paper (PDF, 169 Kb) | Abstract

**2-Fibonacci polynomials in the family of Fibonacci numbers**

*Original research paper. Pages 47—55*

Engin Özkan, Merve Taştan and Ali Aydoğdu

Full paper (PDF, 206 Kb) | Abstract

**On products of quartic polynomials over consecutive indices which are perfect squares**

*Original research paper. Pages 56—61*

Kantaphon Kuhapatanakul, Natnicha Meeboomak and Kanyarat Thongsing

Full paper (PDF, 146 Kb) | Abstract

**Conditions equivalent to the Descartes–Frenicle–Sorli Conjecture on odd perfect numbers – Part II**

*Original research paper. Pages 62—67*

Jose Arnaldo Bebita Dris and Doli-Jane Uvales Tejada

Full paper (PDF, 156 Kb) | Abstract

**The arithmetic derivative and Leibniz-additive functions**

*Original research paper. Pages 68—76*

Pentti Haukkanen, Jorma K. Merikoski and Timo Tossavainen

Full paper (PDF, 162 Kb) | Abstract

**Prime sequences**

*Original research paper. Pages 77—83*

J. V. Leyendekkers and A. G. Shannon

Full paper (PDF, 87 Kb) | Abstract

**One more disproof for the Legendre’s conjecture regarding the prime counting function 𝜋(𝑥)**

*Original research paper. Pages 84—91*

Reza Farhadian and Rafael Jakimczuk

Full paper (PDF, 187 Kb) | Abstract

**An inequality involving a ratio of zeta functions**

*Original research paper. Pages 92—94*

József Sándor

Full paper (PDF, 136 Kb) | Abstract

**On repdigits as product of consecutive Lucas numbers**

*Original research paper. Pages 95—102*

Nurettin Irmak and Alain Togbé

Full paper (PDF, 158 Kb) | Abstract

**Generalized golden ratios and associated Pell sequences**

*Original research paper. Pages 103—110*

A. G. Shannon and J. V. Leyendekkers

Full paper (PDF, 105 Kb) | Abstract

**On two new combined 3-Fibonacci sequences. Part 2**

*Original research paper. Pages 111—114*

Krassimir T. Atanassov

Full paper (PDF, 134 Kb) | Abstract

**Enumeration of 3- and 4-Wilf classes of four 4-letter patterns**

*Original research paper. Pages 115—130*

David Callan and Toufik Mansour

Full paper (PDF, 221 Kb) | Abstract

**Embedding of signed regular graphs**

*Original research paper. Pages 131—141*

Deepa Sinha and Anita Kumari Rao

Full paper (PDF, 211 Kb) | Abstract

**Roman and inverse Roman domination in graphs**

*Original research paper. Pages 142—150*

Zulfiqar Zaman, M. Kamal Kumar and Saad Salman Ahmad

Full paper (PDF, 229 Kb) | Abstract

*This issue of the International Journal “Notes on Number Theory and Discrete Mathematics” is published with the financial support of the Bulgarian National Science Fund, Grant Ref. No. DNP-06-38/2017.*