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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. 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1
LINKS
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.
Sequence in context: A037825 A278701 A188300 * A277154 A011723 A037913
KEYWORD
nonn
AUTHOR
Antti Karttunen, Apr 22 2022
STATUS
approved

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Last modified August 22 06:14 EDT 2024. Contains 375356 sequences. (Running on oeis4.)