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A144741
Number of semiprimes less than or equal to and not coprime to n.
4
0, 0, 0, 1, 0, 2, 0, 2, 2, 3, 0, 4, 0, 4, 4, 4, 0, 6, 0, 5, 5, 5, 0, 8, 3, 6, 4, 7, 0, 10, 0, 6, 6, 7, 6, 11, 0, 8, 7, 11, 0, 14, 0, 9, 9, 9, 0, 14, 4, 12, 8, 10, 0, 15, 7, 12, 9, 10, 0, 20, 0, 11, 11, 11, 8, 19, 0, 12, 10, 18, 0, 19, 0, 12, 14, 13, 8, 21, 0, 17, 9, 13, 0, 24, 9, 14, 11, 17, 0, 28, 9
OFFSET
1,6
EXAMPLE
a(10) = 3: four, six and ten are semiprimes; nine is a semiprime relatively prime to ten.
PROG
(PARI) a(n) = sum(k=1, n, if (bigomega(k) == 2, gcd(k, n) != 1)); \\ Michel Marcus, Apr 15 2023
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Reikku Kulon, Sep 20 2008
STATUS
approved