This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A181471 #28 Dec 21 2024 17:58:47 %S A181471 1,4,8,16,20,34,47,72,95,126,168,208,262,343,433,507,634,799,976,1146, %T A181471 1439,1698,2082,2371,2734 %N A181471 a(n) = number of numbers of the form k^2-1 having n-th prime as largest prime divisor. %C A181471 Theorem: zero does not occur in this sequence. Proof: (p-1)^2-1=(p-2)p. This means that p is greatest prime divisor of (p-1)^2-1 for every p. %C A181471 An effective abc conjecture (c < rad(abc)^2) would imply that a(24)-a(33) are (2371, 2734, 3360, 4022, 4637, 5575, 6424, 7268, 8351, 9661). - _Lucas A. Brown_, Oct 01 2022 %H A181471 Florian Luca and Filip Najman, <a href="https://arxiv.org/abs/1005.1533">On the largest prime factor of x^2-1</a>, arXiv:1005.1533 [math.NT], 2010. %H A181471 Florian Luca and Filip Najman, <a href="https://doi.org/10.1090/S0025-5718-2010-02381-6">On the largest prime factor of x^2-1</a>, Mathematics of Computation 80 (2011), 429-435. (Paper has errata that was posted on the MOC website.) %H A181471 Wikipedia, <a href="https://en.wikipedia.org/wiki/Stormer%27s_theorem">Størmer's theorem</a>. %Y A181471 Row lengths of A223701. %Y A181471 Cf. A039915, A175607. %K A181471 nonn,hard,more %O A181471 1,2 %A A181471 _Artur Jasinski_, Oct 21-22 2010 %E A181471 Wrong terms a(24)-a(25) removed by _Lucas A. Brown_, Oct 01 2022 %E A181471 a(24)-a(25) from _David A. Corneth_, Oct 01 2022