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 A355928 #14 Jul 29 2022 09:53:28 %S A355928 1,3,1,7,6,3,2,15,13,2,3,7,14,6,6,31,2,39,5,42,2,1,6,15,31,42,10,14, %T A355928 30,2,2,7,3,6,3,91,38,15,14,10,42,6,11,21,78,2,3,31,57,93,2,2,6,30,2, %U A355928 30,5,10,15,42,62,6,26,127,21,1,17,14,6,1,2,195,74,114,31,35,6,42,5,186,1,14,21,14,3,33,30,5,10 %N A355928 Squarefree part of the sum of divisors of n. %C A355928 Not multiplicative. %H A355928 Antti Karttunen, <a href="/A355928/b355928.txt">Table of n, a(n) for n = 1..20000</a> %H A355928 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a> %F A355928 a(n) = A007913(A000203(n)). %F A355928 a(n) = A355929(n) + A007913(n). %o A355928 (PARI) A355928(n) = core(sigma(n)); %o A355928 (Python) %o A355928 from sympy.ntheory.factor_ import core, divisor_sigma %o A355928 def A355928(n): return core(divisor_sigma(n)) # _Chai Wah Wu_, Jul 28 2022 %Y A355928 Cf. A000203, A007913, A006532 (positions of 1's), A355929. %Y A355928 Cf. also A080398. %K A355928 nonn %O A355928 1,2 %A A355928 _Antti Karttunen_, Jul 24 2022