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A355453
a(n) = 1 if the third smallest divisor of n is not a prime, otherwise 0.
4
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
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. also A355443, A355454.
Sequence in context: A347519 A160351 A268340 * A336356 A319988 A023969
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jul 02 2022
STATUS
approved