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 A234422 Number of primes <= 123...n. 0
 0, 5, 30, 202, 1474, 11601, 95360, 809227, 7027260, 556442057, 46063874346, 3930144647471, 342720306370180, 30384643585371049, 2728974793135786013, 247673123284120245960, 22671892206713857205404 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA a(n) = A000720(A007908(n)). EXAMPLE There are 1474 primes <= 12345 so a(5) = 1474. MATHEMATICA PrimePi[Table[FromDigits[Flatten[IntegerDigits[Range[n]]]], {n, 12}]] (* Alonso del Arte, Dec 25 2013 *) PROG (Python) def Num(x): ..num = '' ..for n in range(x): ....num += str(n+1) ..return num from sympy import primepi x = 1 while x < 10: ..print(primepi(int(Num(x))), end=', ') ..x += 1 # Edited by Derek Orr, Apr 05 2015 (PARI) s=""; for(n=1, 20, s=concat(s, n); print1(primepi(eval(s)), ", ")) \\ Derek Orr, Apr 05 2015 CROSSREFS Cf. A007908, A000720. Sequence in context: A128328 A245376 A118346 * A091927 A253076 A165312 Adjacent sequences:  A234419 A234420 A234421 * A234423 A234424 A234425 KEYWORD nonn,base,hard,more AUTHOR Derek Orr, Dec 25 2013 EXTENSIONS a(11)-a(12) from Donovan Johnson, Dec 29 2013 a(13)-a(16) from Chai Wah Wu, May 18 2020 a(17) from Chai Wah Wu, May 20 2020 STATUS approved

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Last modified September 28 08:33 EDT 2020. Contains 337394 sequences. (Running on oeis4.)