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 A329879 #9 Sep 12 2020 03:21:10 %S A329879 4,9,24,25,49,54,112,121,150,169,289,294,361,480,529,726,750,841,961, %T A329879 1014,1369,1681,1734,1849,1984,2058,2166,2209,2430,2520,2688,2809, %U A329879 3174,3481,3721,3780,4489,5041,5046,5329,5760,5766,6241,6889,7921,7986,8214,8700 %N A329879 Numbers k such that k and nusigma(k) have the same set of prime divisors, where nusigma(k) is the sum of nonunitary divisors of k (A048146). %C A329879 Numbers k such that rad(nusigma(k)) = rad(k), where rad(k) is the squarefree kernel of k (A007947). %H A329879 Amiram Eldar, <a href="/A329879/b329879.txt">Table of n, a(n) for n = 1..10000</a> %t A329879 rad[n_] := Times @@ (First@# & /@ FactorInteger@ n); usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); nusigma[n_] := DivisorSigma[1, n] - usigma[n]; Select[Range[10^4], rad[nusigma[#]] == rad[#] &] %Y A329879 Cf. A007947, A027598, A048146, A329858. %K A329879 nonn %O A329879 1,1 %A A329879 _Amiram Eldar_, Nov 23 2019