A355453 a(n) = 1 if the third smallest divisor of n is not a prime, otherwise 0.

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

Offset

1

Links

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

Index entries for characteristic functions

Mathematica

a[n_] := If[(f = FactorInteger[n])[[1, 2]] > 1 && (Length[f] == 1 || f[[1, 1]]^2 < f[[2, 1]]), 1, 0]; Array[a, 100] (* Amiram Eldar, Jul 02 2022 *)

Prog

(PARI) A355453(n) = ((n>1) && !isprime(n) && !isprime(divisors(n)[3]));

Crossrefs

Characteristic function of A119315.

Cf. A010051, A292269.

Cf. also A355443, A355454.

Sequence in context: A347519 A160351 A268340 * A336356 A319988 A023969

Adjacent sequences: A355450 A355451 A355452 * A355454 A355455 A355456

Keyword

nonn

Author

Antti Karttunen, Jul 02 2022

Status

approved