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 A322980 a(n) = 1 if n and d(n) are coprime, 0 otherwise. Here d(n) is the number of divisors of n, A000005. 6
 1, 0, 1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1 COMMENTS Equally, a(n) = 1 if and only if n and A049820(n) are coprime. Characteristic function of A046642. LINKS Antti Karttunen, Table of n, a(n) for n = 1..100000 FORMULA a(n) = [A009191(n)==1], where [ ] is the Iverson bracket, and A009191(n) = gcd(n,A000005(n)). MATHEMATICA Table[If[CoprimeQ[n, DivisorSigma[0, n]], 1, 0], {n, 120}] (* Harvey P. Dale, Jul 14 2021 *) PROG (PARI) A322980(n) = (1==gcd(n, numdiv(n))); CROSSREFS Cf. A000005, A009191, A046642, A049820, A322974, A323073. Sequence in context: A120530 A078616 A267800 * A267053 A257477 A259024 Adjacent sequences:  A322977 A322978 A322979 * A322981 A322982 A322983 KEYWORD nonn AUTHOR Antti Karttunen, Jan 05 2019 STATUS approved

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Last modified August 7 23:50 EDT 2022. Contains 355995 sequences. (Running on oeis4.)