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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
A. Frank and 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
Positions of 4's: {0} U A007811.
Cf. A098592.
Sequence in context: A120438 A366470 A192977 * A126712 A162232 A029676
KEYWORD
easy,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 March 28 11:46 EDT 2024. Contains 371241 sequences. (Running on oeis4.)