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A355816
a(n) = 1 if n and sigma(n) are relatively prime, and n has at least two distinct prime factors, otherwise 0.
1
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0
OFFSET
1
FORMULA
a(n) = A143731(n) * A325964(n).
a(n) = [A001221(n) > 1] * [1 == A009194(n)], where [ ] is the Iverson bracket.
MATHEMATICA
a[n_] := If[!PrimePowerQ[n] && CoprimeQ[n, DivisorSigma[1, n]], 1, 0]; a[1] = 0; Array[a, 100] (* Amiram Eldar, Jul 18 2022 *)
PROG
(PARI) A355816(n) = ((omega(n)>1) && (1==gcd(n, sigma(n))));
CROSSREFS
Characteristic function of A095738, numbers that are coprime to sigma but are not prime powers.
Sequence in context: A011736 A085982 A011735 * A353483 A353809 A353808
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jul 18 2022
STATUS
approved