A355443 - OEIS

A355443

a(n) = 1 if n is of the form p^2 * q where p and q are primes with p^2 < q, otherwise 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, 1, 0, 0, 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, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 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, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0

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OFFSET

LINKS

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

Index entries for characteristic functions

FORMULA

a(n) = A353472(n) * A355453(n).

a(n) = A353474(n) - A355444(n).

MATHEMATICA

a[n_] := If[(f = FactorInteger[n])[[;; , 2]] == {2, 1} && f[[1, 1]]^2 < f[[2, 1]], 1, 0]; Array[a, 100] (* Amiram Eldar, Jul 07 2022 *)

PROG

(PARI) A355443(n) = ((numdiv(n) == (3+bigomega(n))) && issquare(divisors(n)[3]));