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 A357497 #9 Oct 03 2022 04:16:49 %S A357497 4,9,12,18,24,25,28,45,49,54,60,90,112,121,126,132,150,153,168,169, %T A357497 198,270,289,294,336,361,364,414,529,560,594,630,637,684,726,841,918, %U A357497 961,1014,1140,1232,1305,1350,1369,1512,1521,1638,1680,1681,1710,1734,1849,1984 %N A357497 Nonsquarefree numbers whose harmonic mean of nonsquarefree divisors in an integer. %C A357497 Analogous to harmonic numbers (A001599) with nonsquarefree divisors. %C A357497 The squares of primes (A001248) are terms since they have a single nonsquarefree divisor. %C A357497 If p is a prime then 6*p^2 is a term. %H A357497 Amiram Eldar, <a href="/A357497/b357497.txt">Table of n, a(n) for n = 1..10000</a> %e A357497 12 is a term since its nonsquarefree divisors are 4 and 12 and their harmonic mean is 6 which is an integer. %t A357497 q[n_] := Length[d = Select[Divisors[n], ! SquareFreeQ[#] &]] > 0 && IntegerQ[HarmonicMean[d]]; Select[Range[2000], q] %Y A357497 Cf. A162296, A322609, A357493, A357494, A357495, A357496. %Y A357497 Subsequence of A013929. %Y A357497 Subsequence: A001248. %Y A357497 Similar sequences: A001599 (harmonic numbers), A006086 (unitary), A063947 (infinitary), A286325 (bi-unitary), A319745 (nonunitary), A335387 (tri-unitary). %K A357497 nonn %O A357497 1,1 %A A357497 _Amiram Eldar_, Oct 01 2022