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 A221945 #19 Sep 08 2022 08:46:04
%S A221945 1,3,7,15,35,79,176,395,883,1976,4419,9882,22097,49410,110485,247052,
%T A221945 552427,1235264,2762135,6176323,13810679,30881617,69053396,154408088,
%U A221945 345266983,772040444,1726334915,3860202221,8631674575,19301011109,43158372875,96505055547,215791864375,482525277735
%N A221945 a(n) = floor(sqrt(2*5^n)).
%C A221945 Floor of norm of (1 + i) * (1 + 2i)^n. - _Jon Perry_, Dec 06 2013
%H A221945 G. C. Greubel, <a href="/A221945/b221945.txt">Table of n, a(n) for n = 0..1000</a>
%t A221945 Table[Floor[Sqrt[2*5^n]],{n,0,40}] (* _Harvey P. Dale_, Feb 10 2016 *)
%o A221945 (PARI) a(n)=sqrtint(2*5^n) \\ _Charles R Greathouse IV_, Apr 18 2013
%o A221945 (Magma) [Floor(Sqrt(2*5^n)): n in [0..40]]; // _G. C. Greubel_, Oct 06 2018
%Y A221945 Cf. A017910, A017913, A017919, A114183, A221718, A221942-A221946.
%K A221945 nonn
%O A221945 0,2
%A A221945 _N. J. A. Sloane_, Feb 01 2013