A353475 a(n) = 1 if n is a semiprime of the form p * q, where p and q are primes with p^2 < q, otherwise 0.

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

Offset

1

Links

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

Index entries for characteristic functions

Formula

a(n) = A064911(n) - A353476(n).

Prog

(PARI) A353475(n) = { my(f=factor(n)); if(#f~ != 2, 0, (1==f[1, 2] && 1==f[2, 2] && (f[1, 1]^2) < f[2, 1])); };

Crossrefs

Characteristic function of A138511, semiprimes where the larger prime factor is greater than the square of the smaller prime factor.

Cf. A064911, A353476.

Sequence in context: A278701 A188300 A380469 * A277154 A011723 A037913

Adjacent sequences: A353472 A353473 A353474 * A353476 A353477 A353478

Keyword

nonn

Author

Antti Karttunen, Apr 22 2022

Status

approved