OFFSET
1,2
LINKS
Michel Marcus, Table of n, a(n) for n = 1..2000
FORMULA
a(n) = A000720(prime(n)^2/2).
MATHEMATICA
a[n_] := PrimePi[Prime[n]^2/2]; Array[a, 55] (* Amiram Eldar, Nov 01 2021 *)
PROG
(PARI) a(n) = primepi(prime(n)^2/2);
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Nov 01 2021
STATUS
approved