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A353476 a(n) = 1 if n is a semiprime of the form p * q, where p and q are (not necessarily distinct) primes with p <= q < p^2, otherwise 0. 3
0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 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, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET
1
LINKS
FORMULA
a(n) = A064911(n) - A353475(n).
PROG
(PARI) A353476(n) = if(2==isprimepower(n), 1, my(f=factor(n)); if(#f~ != 2, 0, (1==f[1, 2] && 1==f[2, 2] && (f[2, 1]) < f[1, 1]^2)));
CROSSREFS
Characteristic function of A251728.
Sequence in context: A072783 A353478 A353555 * A288377 A341609 A064911
KEYWORD
nonn
AUTHOR
Antti Karttunen, Apr 22 2022
STATUS
approved

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Last modified March 28 13:19 EDT 2024. Contains 371254 sequences. (Running on oeis4.)