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A289493
Number of primes in the interval [2n, 3n].
9
2, 1, 1, 1, 2, 2, 2, 3, 2, 2, 3, 2, 3, 4, 4, 4, 4, 5, 4, 5, 5, 4, 5, 5, 6, 6, 6, 7, 7, 7, 6, 6, 7, 7, 8, 8, 8, 9, 9, 8, 8, 7, 8, 9, 8, 9, 10, 10, 9, 10, 10, 9, 10, 9, 9, 10, 9, 10, 10, 11, 12, 12, 12, 12, 13, 13, 14, 14, 13, 12, 13, 13, 13, 13, 13, 13, 14, 15, 14, 15
OFFSET
1,1
LINKS
Mohamed El Bachraoui, Primes in the interval [2n, 3n] (2006)
FUNG Cheok Yin, C++ program
FORMULA
a(n) = A000720(3n) - A000720(2n), for n > 1. - M. F. Hasler, Sep 29 2019
PROG
(PARI) A289493(n)=primepi(3*n)-if(n>1, primepi(2*n)) \\ M. F. Hasler, Sep 29 2019
CROSSREFS
Cf. A000720 (PrimePi), A101985 (numbers occurring here exactly once).
Sequence in context: A282904 A299825 A362756 * A324341 A271325 A228431
KEYWORD
nonn
AUTHOR
FUNG Cheok Yin, Jul 07 2017
STATUS
approved