A353799 a(n) = 1 if the number of divisors of n is not larger than 4, otherwise 0.

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

Offset

1

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for characteristic functions

Index entries for sequences computed from exponents in factorization of n

Formula

a(n) = [A000005(n) <= 4], where [ ] is the Iverson bracket.

a(n) = [A101296(n) <= 5].

For n > 1, a(n) = A302048(n) + A353788(n).

Mathematica

a[n_] := If[DivisorSigma[0, n] <= 4, 1, 0]; Array[a, 120] (* Amiram Eldar, May 13 2022 *)

Prog

(PARI) A353799(n) = (4>=numdiv(n));

Crossrefs

Characteristic function of A007964.

Cf. A000005, A101296, A302048, A353788.

Sequence in context: A103447 A354923 A354924 * A123927 A089829 A294935

Adjacent sequences: A353796 A353797 A353798 * A353800 A353801 A353802

Keyword

nonn

Author

Antti Karttunen, May 13 2022

Status

approved