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 A038800 Number of primes between 10n and 10n+9. 9
 4, 4, 2, 2, 3, 2, 2, 3, 2, 1, 4, 1, 1, 3, 1, 2, 2, 2, 1, 4, 0, 1, 3, 2, 1, 2, 2, 2, 2, 1, 1, 3, 0, 2, 2, 2, 1, 2, 2, 1, 2, 1, 1, 3, 2, 1, 3, 1, 1, 2, 2, 0, 2, 0, 2, 1, 2, 2, 1, 2, 2, 3, 0, 1, 3, 2, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 1, 1, 1, 1, 4, 1, 0, 3, 1, 1, 3, 0, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 3, 1, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS If n runs through the primes, the subsequence 2, 2, 2, 3, 1, 3, 2, 4, 2, 1, 3, 2, 1, 3, 1, 0, 2, 3, 2,... is created. - R. J. Mathar, Jul 19 2012 Since 431, 433, and 439 are all prime, a(43)=3. - Bobby Jacobs, Sep 25 2016 LINKS Michael De Vlieger, Table of n, a(n) for n = 0..10000 A. Frank & P. Jacqueroux, International Contest, 2001. Numerators of Item 23 MATHEMATICA Table[Count[Range[10 n, 10 n + 9], p_ /; PrimeQ@ p], {n, 0, 105}] (* Michael De Vlieger, Sep 25 2016 *) PROG (PARI) a(n) = primepi(10*n+9) - primepi(10*n); \\ Michel Marcus, Sep 26 2016 CROSSREFS Cf. A055781, A055782, A055783, A055784. Sequence in context: A193556 A120438 A192977 * A126712 A162232 A029676 Adjacent sequences: A038797 A038798 A038799 * A038801 A038802 A038803 KEYWORD nonn AUTHOR EXTENSIONS a(43) corrected by Bobby Jacobs, Sep 25 2016 a(101) and a(104) corrected by Michael De Vlieger, Sep 25 2016 STATUS approved

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Last modified November 29 18:13 EST 2022. Contains 358431 sequences. (Running on oeis4.)