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 A065857 The (10^n)-th composite number. 3
 4, 18, 133, 1197, 11374, 110487, 1084605, 10708555, 106091745, 1053422339, 10475688327, 104287176419, 1039019056246, 10358018863853, 103307491450820, 1030734020030318, 10287026204717358, 102692313540015924, 1025351434864118026, 10239531292310798956, 102270102190290407386 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 REFERENCES A. E. Bojarincev, Asymptotic expressions for the n-th composite number. Univ. Mat. Zap. 6:21-43(1967). [in Russian] J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 133, p. 45, Ellipses, Paris 2008. LINKS Chai Wah Wu, Table of n, a(n) for n = 0..22 Laurentiu Panaitopol, Some properties of the series of composed [sic] numbers, Journal of Inequalities in Pure and Applied Mathematics 2:3 (2001). J. Barkley Rosser and Lowell Schoenfeld, Approximate formulas for some functions of prime numbers. Illinois J. Math. 6 (1962), pp. 64-94. FORMULA a(n) = A002808(A011557(n)). a(n) = 10^(n + n/log n + 2n/log^2 + 4n/log^3 n + O(n/log^4 n)). See Bojarincev for an asymptotic expansion. - Charles R Greathouse IV, May 30 2013 EXAMPLE The 100th composite number is C(100)=133, while the 100th prime is 541. In general: A000720(m) < A062298(m) < m < A002808(m) < A000040(m), for example pi(100)=25 < 75 < 100 < C(100)=133 < prime(100)=541. MATHEMATICA Composite[n_Integer] := Block[ {k = n + PrimePi[n] + 1 }, While[ k != n + PrimePi[k] + 1, k = n + PrimePi[k] + 1]; Return[k]]; Table[Composite[10^n], {n, 0, 9}] PROG (PARI) a(n)=my(k=10^n); forcomposite(n=4, 2*k+2, if(k--==0, return(n))) \\ Charles R Greathouse IV, May 30 2013 CROSSREFS Cf. A033844, A002808, A062298, A000720, A006988, A065855, A065856. Sequence in context: A034517 A294462 A194559 * A214647 A156445 A304997 Adjacent sequences:  A065854 A065855 A065856 * A065858 A065859 A065860 KEYWORD nonn,hard AUTHOR Labos Elemer, Nov 26 2001 EXTENSIONS More terms from Robert G. Wilson v, Nov 26 2001 a(14) from Lekraj Beedassy, Jul 14 2008 a(15)-a(19) from Chai Wah Wu, Apr 16 2018 a(20) from Chai Wah Wu, Aug 23 2018 STATUS approved

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Last modified February 19 01:03 EST 2020. Contains 332028 sequences. (Running on oeis4.)