A221945 - OEIS

%I #19 Sep 08 2022 08:46:04

%S 1,3,7,15,35,79,176,395,883,1976,4419,9882,22097,49410,110485,247052,

%T 552427,1235264,2762135,6176323,13810679,30881617,69053396,154408088,

%U 345266983,772040444,1726334915,3860202221,8631674575,19301011109,43158372875,96505055547,215791864375,482525277735

%N a(n) = floor(sqrt(2*5^n)).

%C Floor of norm of (1 + i) * (1 + 2i)^n. - _Jon Perry_, Dec 06 2013

%H G. C. Greubel, <a href="/A221945/b221945.txt">Table of n, a(n) for n = 0..1000</a>

%t Table[Floor[Sqrt[2*5^n]],{n,0,40}] (* _Harvey P. Dale_, Feb 10 2016 *)

%o (PARI) a(n)=sqrtint(2*5^n) \\ _Charles R Greathouse IV_, Apr 18 2013

%o (Magma) [Floor(Sqrt(2*5^n)): n in [0..40]]; // _G. C. Greubel_, Oct 06 2018

%Y Cf. A017910, A017913, A017919, A114183, A221718, A221942-A221946.

%K nonn

%O 0,2

%A _N. J. A. Sloane_, Feb 01 2013