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A086693 Number of primes less than prime(n)^prime(n). 0
2, 9, 445, 65685, 11262113374, 9373678643933, 17547676024364306476, 36020106660104388871845 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..8.

FORMULA

a(n) = A064151(prime(n)) = A000720(A051674(n)). - Michel Marcus, Mar 17 2015

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

Cf. A064151.

Sequence in context: A024225 A266289 A000883 * A085605 A180936 A036878

Adjacent sequences:  A086690 A086691 A086692 * A086694 A086695 A086696

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

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Last modified February 16 08:26 EST 2019. Contains 320159 sequences. (Running on oeis4.)