A355938 a(n) = 1 if sigma(n^2) is a noncomposite, otherwise 0.

1, 1, 1, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 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, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1

Offset

1

Links

Antti Karttunen, Table of n, a(n) for n = 1..100000

Index entries for characteristic functions

Formula

a(n) = A080339(A000203(n^2)) = A080339(A065764(n)).

For all n >= 1, a(n) <= A010055(n).

Mathematica

a[n_] := If[!CompositeQ[DivisorSigma[1, n^2]], 1, 0]; Array[a, 100] (* Amiram Eldar, Jul 21 2022 *)

Prog

(PARI) A355938(n) = ((1==n)||isprime(sigma(n^2)));

Crossrefs

Characteristic function of {1} UNION A055638.

Cf. A000203, A010055, A065764, A080339.

Cf. also A355937.

Sequence in context: A059318 A071029 A071030 * A268240 A104037 A014044

Adjacent sequences: A355935 A355936 A355937 * A355939 A355940 A355941

Keyword

nonn

Author

Antti Karttunen, Jul 21 2022

Status

approved