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 A384411 #35 Jun 20 2025 08:14:22 %S A384411 26,46,296,586 %N A384411 Pairs (k, m) such that k = sigma(m) - m and m = sigma(2*k) - 2*k. %C A384411 Fixed points of x->A346878(A001065(x)). %C A384411 Next term > 15*10^7. %H A384411 S. I. Dimitrov, <a href="https://arxiv.org/abs/2408.07387">Generalizations of amicable numbers</a>, arXiv:2408.07387 [math.NT], 2024. %e A384411 (26, 46) is such a pair because 26 = sigma(46) - 46 and 46 = sigma(52) - 52. %e A384411 (296, 586) is another pair. %o A384411 (PARI) for(k=1,10^9, m = sigma(2*k) - 2*k;if(k == sigma(m) - m, print1(k, ", ", m, ", "))); \\ _Joerg Arndt_, Jun 01 2025 %Y A384411 Cf. A000203, A001065, A063990, A259180, A346878, A383483. %K A384411 nonn,hard,more %O A384411 1,1 %A A384411 _S. I. Dimitrov_, Jun 01 2025