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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
OFFSET
1
COMMENTS
Equally, a(n) = 1 if and only if n and A049820(n) are coprime.
Characteristic function of A046642.
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
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jan 05 2019
STATUS
approved