A322980 a(n) = 1 if n and d(n) are coprime, 0 otherwise. Here d(n) is the number of divisors of n, A000005.

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

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

Index entries for characteristic functions

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 A359591 A359592

Adjacent sequences: A322977 A322978 A322979 * A322981 A322982 A322983

Keyword

nonn

Author

Antti Karttunen, Jan 05 2019

Status

approved