OFFSET
1,4
FORMULA
a(n) = pi(2n - 3) - 1 for n > 2 with a(1) = a(2) = 0.
MAPLE
with(numtheory): a:=n->`if`(n<3, 0, pi(2*n-3)-1): seq(a(n), n=1..100);
MATHEMATICA
Table[If[n < 3, 0, PrimePi[2n - 3] - 1], {n, 100}]
PROG
(Magma) [0, 0] cat [#PrimesUpTo(2*n-3)-1: n in [3..80]]; // Vincenzo Librandi, Nov 24 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Nov 23 2016
STATUS
approved