Dąbrowski's conjecture on smooth numbers of the form x^2-1

Let p1=2,p2=3,p3=5,,pkp_1=2,p_2=3,p_3=5,\ldots,p_k be the first kk primes. For positive integers xx and nonnegative integers α1,,αk\alpha_1,\ldots,\alpha_k, consider the Diophantine equation

x21=p1α1pkαk.x^2-1=p_1^{\alpha_1}\cdots p_k^{\alpha_k}.

Dąbrowski's conjecture. The equation has exactly 2828 solutions (x;α1,,αk)(x;\alpha_1,\ldots,\alpha_k) in positive integers, namely the solutions listed in the statement: (3;3)(3;3); (5;3,1),(7;4,1),(17;5,2)(5;3,1),(7;4,1),(17;5,2); (11;3,1,1),(19;3,2,1),(31;6,1,1),(49;5,1,2),(161;6,4,1)(11;3,1,1),(19;3,2,1),(31;6,1,1),(49;5,1,2),(161;6,4,1); (29;3,1,1,1),(41;4,1,1,1),(71;4,2,1,1),(251;3,2,3,1),(449;7,2,2,1),(4801;7,1,2,4),(8749;3,7,4,1)(29;3,1,1,1),(41;4,1,1,1),(71;4,2,1,1),(251;3,2,3,1),(449;7,2,2,1),(4801;7,1,2,4),(8749;3,7,4,1); (769;9,1,1,1,1),(881;5,2,1,2,1),(1079;4,3,1,2,1),(6049;6,3,2,1,2),(19601;5,4,2,2,2)(769;9,1,1,1,1),(881;5,2,1,2,1),(1079;4,3,1,2,1),(6049;6,3,2,1,2),(19601;5,4,2,2,2); (3431;4,1,1,3,1,1),(4159;7,3,1,1,1,1),(246401;8,6,2,1,1,2)(3431;4,1,1,3,1,1),(4159;7,3,1,1,1,1),(246401;8,6,2,1,1,2); (1429;3,1,1,1,1,1,1),(24751;5,2,3,1,1,1,1),(388961;6,4,1,4,1,1,1)(1429;3,1,1,1,1,1,1),(24751;5,2,3,1,1,1,1),(388961;6,4,1,4,1,1,1); and (1267111;4,3,1,1,3,1,1,2)(1267111;4,3,1,1,3,1,1,2).

This conjecture asks for a complete determination of the solutions whose value x21x^2-1 has no prime factors beyond the first kk primes. The source attributes the formulation to Dąbrowski; the provided text gives no evidence that the conjecture has been proved or disproved.

Sources & referencesView supporting material

Primary source

Florian Luca and Filip Najman, “On the largest prime factor of x^2-1”, arXiv:1005.1533 (2010).

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