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
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