OFFSET
1,1
LINKS
John Cerkan, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
For example a(5)=4 because between 5 and 15 there are 4 primes: 5, 7, 11 and 13.
MATHEMATICA
Array[Count[Range[#, 3 #], k_ /; PrimeQ@ k] &, 76] (* Michael De Vlieger, Mar 20 2017 *)
PROG
(PARI) a(n) = primepi(3*n) - primepi(n-1); \\ Michel Marcus, Sep 28 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Erich Friedman
STATUS
approved