A234317 Number of primes <= R_n where R_n is 11...111 with n 1's.

0, 5, 29, 186, 1345, 10544, 86537, 733409, 6363181, 56196113, 503193256, 4555800188, 41621368073, 383118399785, 3549047966156, 33056584174789, 309353882390965, 2907021742443974, 27417323062119920, 259423936749134301, 2461813897281353729, 23422580231698331834

Offset

1,2

Links

David Baugh, Table of n, a(n) for n = 1..26 (terms n = 16..26 found with Kim Walisch's primecount program).

Formula

a(n) = A000720(R_n) = A000720(A002275(n)) where R_n is 11...111 with n 1's.

Example

There are 1345 primes less than or equal to 11111. Thus a(5) = 1345.

Mathematica

PrimePi/@Table[FromDigits[PadRight[{}, n, 1]], {n, 15}] (* The program will take a long time to run *) (* Harvey P. Dale, Jan 21 2015 *)

Prog

(Python)
import sympy
from sympy import primepi
for n in range(1, 50):
..print(primepi((10**n-1)/9), end=', ')
(PARI) a(n)=primepi(10^n\9) \\ Charles R Greathouse IV, Apr 30 2014

Crossrefs

Cf. A000720, A002275.

Sequence in context: A127846 A059231 A137573 * A346845 A367232 A078945

Adjacent sequences: A234314 A234315 A234316 * A234318 A234319 A234320

Keyword

nonn,less

Author

Derek Orr, Dec 23 2013

Extensions

a(14)-a(15) from Hiroaki Yamanouchi, Sep 27 2014

a(16)-a(22) from David Baugh, Sep 29 2020

Status

approved