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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 (list; graph; refs; listen; history; text; internal format)
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
Ceiling[LogIntegral[Range[2, 70]]] (* Harvey P. Dale, Dec 29 2012 *)
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
Cf. A047783 (floor), A047784 (round).
Sequence in context: A005185 A119466 A100922 * A027923 A167743 A020888
KEYWORD
nonn
AUTHOR
STATUS
approved

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Last modified May 24 12:09 EDT 2024. Contains 372773 sequences. (Running on oeis4.)