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 A329880 Numbers k such that the sums of unitary and nonunitary divisors of k have the same set of prime divisors. 1
 24, 40, 56, 76, 88, 104, 108, 116, 120, 136, 152, 168, 184, 228, 232, 236, 248, 261, 264, 280, 296, 312, 316, 328, 342, 344, 348, 356, 376, 380, 408, 424, 436, 440, 456, 472, 488, 520, 522, 531, 532, 536, 540, 552, 556, 568, 580, 584, 596, 616, 632, 664, 680 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers k such that rad(usigma(k)) = rad(nusigma(k)), where rad(k) is the squarefree kernel of k (A007947), usigma(k) is the sum of unitary divisors of k (A034448) and nusigma(k) = sigma(k) - usigma(k) is the sum of nonunitary divisors of k (A048146). Numbers k such that rad(usigma(k)) = rad(nusigma(k)) = rad(k) are 24, 3780, 26460, ... with no other term below 3*10^9. LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 MATHEMATICA 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[700], rad[usigma[#]] == rad[nusigma[#]] &] CROSSREFS Cf. A007947, A034448, A048146, A329858, A329879. Sequence in context: A297401 A065127 A065036 * A303359 A340747 A340746 Adjacent sequences: A329877 A329878 A329879 * A329881 A329882 A329883 KEYWORD nonn AUTHOR Amiram Eldar, Nov 23 2019 STATUS approved

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Last modified September 7 07:38 EDT 2024. Contains 375729 sequences. (Running on oeis4.)