cp's OEIS Frontend

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.

A358022 Least odd number m such that m*2^n is an amicable number, and -1 if no such number exists.

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%I A358022 #27 Nov 17 2022 16:44:09
%S A358022 12285,605,55,779,1081,37,119957,73153,2927269,239,25329329,7230607,
%T A358022 964119281,66445153,7613527,18431675687,328796066369,264003743,
%U A358022 11298797322497,59592560831,949755039781,2759891672513
%N A358022 Least odd number m such that m*2^n is an amicable number, and -1 if no such number exists.
%C A358022 Similar to A358320 but restricted to amicable numbers.
%H A358022 Sergei Chernykh, <a href="https://sech.me/boinc/Amicable/">Amicable Numbers</a>.
%o A358022 (PARI) f(m) = if (m, sigma(m)-m, 0);
%o A358022 fpm(p, m) = (2*p-1)*sigma(m) - p*m;
%o A358022 a(n) = my(p=2^n); forstep(m=1, +oo, 2, my(x=fpm(p,m)); if ((x!=p*m) && (f(x) == p*m), return(m)));
%Y A358022 Cf. A001065, A002025, A259180, A262625, A358320.
%K A358022 nonn,more
%O A358022 0,1
%A A358022 _Michel Marcus_, Nov 17 2022
%E A358022 a(12)-a(22) were calculated using Chernykh's database by _Amiram Eldar_, Nov 17 2022