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 A121855 #18 Aug 09 2015 02:19:32
%S A121855 0,4,5,6,7,8,8,9,9,10,10,11,11,12,12,13,13,13,14,14,15,15,15,16,16,16,
%T A121855 17,17,17,17,18,18,18,19,19,19,19,20,20,20,20,21,21,21,21,22,22,22,22,
%U A121855 22,23,23,23,23,24,24,24,24,24,25,25,25,25,25,26,26,26,26,26,27,27,27
%N A121855 a(n) = ceiling(Pi*sqrt(n)).
%H A121855 Vincenzo Librandi, <a href="/A121855/b121855.txt">Table of n, a(n) for n = 0..1000</a> (indices changed and term 1000 added by Ivan Panchenko)
%t A121855 Table[Ceiling[Pi Sqrt[n]], {n, 0, 100}] (* _Vincenzo Librandi_, Feb 21 2013 *)
%Y A121855 Cf. A121275, A121276.
%K A121855 nonn,easy
%O A121855 0,2
%A A121855 _Mohammad K. Azarian_, Aug 30 2006
%E A121855 Offset corrected by _Ivan Panchenko_, Nov 13 2013