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 A080403 #11 Dec 30 2024 03:17:56
%S A080403 1,2,4,5,8,9,13,16,18,20,25,29,37,49,50,61,64,72,73,80,101,109,113,
%T A080403 116,117,121,122,128,137,144,148,169,173,181,200,208,218,229,242,244,
%U A080403 261,277,281,289,292,313,317,320,325,333,353,362,373,389,397,401,404,409
%N A080403 Numbers n such that both A000203(n) and A001157(n) are squarefree: sum of divisors and squares of divisors of n are squarefree.
%H A080403 Amiram Eldar, <a href="/A080403/b080403.txt">Table of n, a(n) for n = 1..10000</a>
%t A080403 Do[s1=MoebiusMu[DivisorSigma[1, n]]; s2=MoebiusMu[DivisorSigma[2, n]]; If[ !Equal[s1, 0]&&!Equal[s2, 0], Print[n]], {n, 1, 1000}]
%Y A080403 Cf. A001157, A000203, A065300, A080401, A080402.
%K A080403 easy,nonn
%O A080403 1,2
%A A080403 _Labos Elemer_, Mar 19 2003