This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A047785 #15 Sep 08 2022 08:44:57 %S A047785 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, %T A047785 14,14,14,14,15,15,15,16,16,16,16,17,17,17,17,18,18,18,18,19,19,19,19, %U A047785 20,20,20,20,21,21,21,21,22,22,22,22,23,23,23,23,24 %N A047785 a(n) = ceiling(Li(n)). %D A047785 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. %H A047785 Harvey P. Dale, <a href="/A047785/b047785.txt">Table of n, a(n) for n = 2..1000</a> %H A047785 M. Abramowitz and I. A. Stegun, eds., <a href="http://www.convertit.com/Go/ConvertIt/Reference/AMS55.ASP">Handbook of Mathematical Functions</a>, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy]. %F A047785 a(n) = ceiling(logarithmic integral(n)). - _G. C. Greubel_, May 17 2019 %t A047785 Ceiling[LogIntegral[Range[2,70]]] (* _Harvey P. Dale_, Dec 29 2012 *) %o A047785 (PARI) vector(80, n, n++; ceil(real(-eint1(-log(n)))) ) \\ _G. C. Greubel_, May 17 2019 %o A047785 (Magma) [Ceiling(LogIntegral(n)): n in [2..80]]; // _G. C. Greubel_, May 17 2019 %o A047785 (Sage) [ceil(li(n)) for n in (2..80)] # _G. C. Greubel_, May 17 2019 %Y A047785 Cf. A047783 (floor), A047784 (round). %K A047785 nonn %O A047785 2,1 %A A047785 _N. J. A. Sloane_