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 A385654 #9 Jul 13 2025 19:22:01 %S A385654 2,2,2,3,3,3,3,3,3,3,3,5,5,5,5,5,5,5,5,5,7,7,7,7,7,7,7,7,7,7,7,7,7,7, %T A385654 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, %U A385654 7,7,7,13,13,13,13,13,7,13,13,13,13,13,13 %N A385654 Greatest prime factor of A385653(n). %C A385654 A number appears in this sequence if and only if it is a uniquely popular prime; see A289662. a(n) is uniquely popular on the interval [2,A385653(n)]. %H A385654 Pontus von Brömssen, <a href="/A385654/b385654.txt">Table of n, a(n) for n = 1..10000</a> %o A385654 (PARI) gpf(n) = if (n==1,1, vecmax(factor(n)[,1])); \\ A006530 %o A385654 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 A385654 a(n) = my(k=2); while (f(k) !=n, k++); gpf(k); \\ _Michel Marcus_, Jul 06 2025 %Y A385654 Cf. A006530, A289662, A385503, A385652, A385653. %K A385654 nonn %O A385654 1,1 %A A385654 _Pontus von Brömssen_, Jul 06 2025