A038800 Number of primes between 10n and 10n+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

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 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

Cf. A055781, A055782, A055783, A055784.

Positions of 4's: {0} U A007811.

Cf. A098592.

Sequence in context: A120438 A366470 A192977 * A126712 A162232 A029676

Adjacent sequences: A038797 A038798 A038799 * A038801 A038802 A038803

Keyword

easy,nonn

Author

Jeff Burch

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