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 A386726 #26 Aug 06 2025 18:18:50 %S A386726 2,238,280,308,310,382,790,795,920,952,1034,1162,1246,1330,1410,1434, %T A386726 2002,2024,2506,2632,2728,2750,2926,3040,3210,3452,3496,3500,3630, %U A386726 4134,4260,4466,4550,4968,5080,5278,5396,5520,5530,5756,6128,6230,6426,6888,7288,7584,7640,7910,7990 %N A386726 Numbers x such that there exist two integers 0<x<=y<=z such that sigma(x) = sigma(y) = sigma(z) = (x + y + z)/2. %C A386726 The numbers x, y and z form an amicable triple according to Yanney's definition. %H A386726 Max Alekseyev, <a href="https://oeis.org/wiki/User:Max_Alekseyev/gpscripts">PARI/GP Scripts for Miscellaneous Math Problems</a> (invphi.gp). %H A386726 Benjamin Franklin Yanney, <a href="https://www.jstor.org/stable/2300268">Another definition of amicable numbers and some of their relations to Dickson's amicables</a>, Amer. Math. Monthly, Vol. 30, No. 6 (1923), 311-315. %e A386726 238 is in the sequence since sigma(238) = sigma(255) = sigma(371) = 432 = (238 + 255 + 371)/2. %o A386726 (PARI) isok(x1) = my(s=sigma(x1), vx=select(x->(x>=x1), invsigma(s)), v=vector(3, i, vx[1])); for (i=1, #vx, v[2] = vx[i]; for (j=1, #vx, v[3] = vx[j]; if (vecsum(v) == 2*s, return(1)););); \\ _Michel Marcus_, Aug 01 2025 %Y A386726 Cf. A000203, A125490, A386727. %K A386726 nonn %O A386726 1,1 %A A386726 _S. I. Dimitrov_, Jul 31 2025 %E A386726 More terms from _Michel Marcus_, Aug 01 2025