OFFSET
1,1
FORMULA
EXAMPLE
There are 9 primes less than 3^3 = 27, namely 2,3,5,7,11,13,17,19,23. Since 3 is prime(2), a(2) = 9.
MATHEMATICA
f[n_] := Block[{p = Prime@ n}, PrimePi[p^p]]; Array[f, 5] (* Michael De Vlieger, Mar 17 2015 *)
PROG
(PARI) primeslesspp(n) = /* primes less than p^p */ { forprime(x=2, n, y=primepi(x^x); print1(y", "); ); }
(Magma) [ #PrimesUpTo(NthPrime(n)^NthPrime(n)): n in [1..4] ]; // Vincenzo Librandi, Mar 17 2015
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Cino Hilliard, Jul 28 2003
EXTENSIONS
a(5)-a(7) from David Baugh, Mar 17 2015
a(8) from Chai Wah Wu, Apr 18 2018
STATUS
approved