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 A080403 Numbers n such that both A000213(n) and A001157(n) are squarefree: sum of divisors and squares of divisors of n are squarefree. 1
 1, 2, 4, 5, 8, 9, 13, 16, 18, 20, 25, 29, 37, 49, 50, 61, 64, 72, 73, 80, 101, 109, 113, 116, 117, 121, 122, 128, 137, 144, 148, 169, 173, 181, 200, 208, 218, 229, 242, 244, 261, 277, 281, 289, 292, 313, 317, 320, 325, 333, 353, 362, 373, 389, 397, 401, 404, 409 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 MATHEMATICA Do[s1=MoebiusMu[DivisorSigma[1, n]]; s2=MoebiusMu[DivisorSigma[2, n]]; If[ !Equal[s1, 0]&&!Equal[s2, 0], Print[n]], {n, 1, 1000}] CROSSREFS Cf. A001157, A000213, A065300, A080401, A080402. Sequence in context: A143989 A064573 A065300 * A280050 A271392 A195364 Adjacent sequences:  A080400 A080401 A080402 * A080404 A080405 A080406 KEYWORD easy,nonn AUTHOR Labos Elemer, Mar 19 2003 STATUS approved

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Last modified May 28 14:47 EDT 2020. Contains 334684 sequences. (Running on oeis4.)