

A047785


a(n) = ceiling(Li(n)).


3



2, 3, 3, 4, 5, 5, 6, 6, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 10, 11, 11, 11, 12, 12, 12, 13, 13, 13, 14, 14, 14, 14, 15, 15, 15, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 22, 22, 22, 22, 23, 23, 23, 23, 24
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OFFSET

2,1


REFERENCES

M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 238.


LINKS

M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].


FORMULA

a(n) = ceiling(logarithmic integral(n)).  G. C. Greubel, May 17 2019


MATHEMATICA



PROG

(PARI) vector(80, n, n++; ceil(real(eint1(log(n)))) ) \\ G. C. Greubel, May 17 2019
(Magma) [Ceiling(LogIntegral(n)): n in [2..80]]; // G. C. Greubel, May 17 2019
(Sage) [ceil(li(n)) for n in (2..80)] # G. C. Greubel, May 17 2019


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



