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 A385653 #11 Jul 13 2025 19:21:52 %S A385653 2,4,8,12,18,24,27,36,48,54,72,80,90,100,120,125,135,150,160,180,196, %T A385653 210,224,245,252,280,294,315,336,343,350,378,392,420,441,448,490,504, %U A385653 525,560,567,588,630,672,686,700,735,756,784,840,875,882,896,945,980 %N A385653 Least k such that A385652(k) = n. %C A385653 A385654(n) is uniquely popular on the interval [2,a(n)]; see A289662. %C A385653 Equivalently, a(n) is the least k >= 2 such that A078899(k) = n. %H A385653 Pontus von Brömssen, <a href="/A385653/b385653.txt">Table of n, a(n) for n = 1..10000</a> %o A385653 (PARI) gpf(n) = if (n==1,1, vecmax(factor(n)[,1])); \\ A006530 %o A385653 f(n) = my(v=vector(n, k, gpf(k)), s=Set(v)); vecmax(apply(x->#x, vector(#s, i, select(x->(x==s[i]), v)))); \\ A385652 %o A385653 a(n) = my(k=2); while (f(k) !=n, k++); k; \\ _Michel Marcus_, Jul 06 2025 %Y A385653 Cf. A006530, A078899, A289662, A385503, A385652, A385654. %K A385653 nonn %O A385653 1,1 %A A385653 _Pontus von Brömssen_, Jul 06 2025