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 A072697 #16 Sep 08 2022 08:45:06 %S A072697 2,3,5,7,11,13,15,17,19,21,23,29,31,33,35,37,39,41,42,43,47,51,53,55, %T A072697 57,59,61,65,67,69,71,73,77,78,79,83,85,87,89,91,93,95,97,101,103,105, %U A072697 107,109,110,111,113,114,115,119,123,127,129,131,133,137,139,141,143 %N A072697 Squarefree numbers such that the sum of the prime factors is a multiple of the number of prime factors. %H A072697 Amiram Eldar, <a href="/A072697/b072697.txt">Table of n, a(n) for n = 1..10000</a> %e A072697 42=2*3*7: number of factors = 3 and sum of factors =2+3+7=12, as 12=4*3, 42 is a term: a(19)=42, A072698(19)=3, A072699(19)=12 and A072700(19)=4 contributes 1 count for A072701(4), as (2+3+7)/3=4. %t A072697 Select[ Range[2, 143], SquareFreeQ[#] && Divisible[ Tr[ fi = FactorInteger[#][[All, 1]]], Length[fi]]& ](* _Jean-François Alcover_, Jul 11 2012 *) %o A072697 (Magma) [k:k in [2..200]| IsSquarefree(k) and IsIntegral(&+PrimeDivisors(k)/#PrimeDivisors(k))]; // _Marius A. Burtea_, Nov 14 2019 %Y A072697 Cf. A005117, A072700, A072701, A072698, A072699. %K A072697 nonn %O A072697 1,1 %A A072697 _Reinhard Zumkeller_, Jul 04 2002