This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A234317 Number of primes <= R_n where R_n is 11...111 with n 1's. 0
 0, 5, 29, 186, 1345, 10544, 86537, 733409, 6363181, 56196113, 503193256, 4555800188, 41621368073, 383118399785, 3549047966156 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS 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 * A078945 A113713 A142980 Adjacent sequences:  A234314 A234315 A234316 * A234318 A234319 A234320 KEYWORD nonn,more,less AUTHOR Derek Orr, Dec 23 2013 EXTENSIONS a(14)-a(15) from Hiroaki Yamanouchi, Sep 27 2014 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified March 20 07:27 EDT 2019. Contains 321345 sequences. (Running on oeis4.)