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AN IMPROVEMENT TO A THEOREM OF LEONETTI AND LUCA

Published online by Cambridge University Press:  01 September 2023

TRAN NGUYEN THANH DANH
Affiliation:
VNU-HCM High School for the Gifted Students, Ho Chi Minh City, Vietnam e-mail: danhtran17022005@gmail.com
HOANG TUAN DUNG
Affiliation:
Hanoi National University of Education High School for the Gifted Students, Hanoi, Vietnam e-mail: tuandunghg01@gmail.com
PHAM VIET HUNG
Affiliation:
HUS High School for Gifted Students, Hanoi, Vietnam e-mail: vhpro2005@gmail.com
NGUYEN DINH KIEN
Affiliation:
Tran Phu High School for the Gifted Students, Haiphong, Vietnam e-mail: kien08022006@gmail.com
NGUYEN AN THINH
Affiliation:
Tran Phu High School for the Gifted Students, Haiphong, Vietnam e-mail: thinhyte0x0@gmail.com
KHUC DINH TOAN
Affiliation:
Bac Ninh High School for the Gifted Students, Báˇc Ninh, Vietnam e-mail: khucdinhtoan985@gmail.com
NGUYEN XUAN THO*
Affiliation:
School of Applied Mathematics and Informatics, Hanoi University of Science and Technology, Hanoi, Vietnam

Abstract

Leonetti and Luca [‘On the iterates of the shifted Euler’s function’, Bull. Aust. Math. Soc., to appear] have shown that the integer sequence $(x_n)_{n\geq 1}$ defined by $x_{n+2}=\phi (x_{n+1})+\phi (x_{n})+k$, where $x_1,x_2\geq 1$, $k\geq 0$ and $2 \mid k$, is bounded by $4^{X^{3^{k+1}}}$, where $X=(3x_1+5x_2+7k)/2$. We improve this result by showing that the sequence $(x_n)$ is bounded by $2^{2X^2+X-3}$, where $X=x_1+x_2+2k$.

Type
Research Article
Copyright
© The Author(s), 2023. Published by Cambridge University Press on behalf of Australian Mathematical Publishing Association Inc.

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Footnotes

Nguyen Xuan Tho is funded by the Vietnam Ministry of Education and Training under the project number B2022-CTT-03.

References

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Leonetti, P. and Luca, F., ‘On the iterates of the shifted Euler’s function’, Bull. Aust. Math. Soc., to appear. Published online (12 May 2023).CrossRefGoogle Scholar
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