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 A017961 #17 Sep 08 2022 08:44:43
%S A017961 1,4,19,82,361,1573,6859,29897,130321,568056,2476099,10793065,
%T A017961 47045881,205068240,893871739,3896296578,16983563041,74029634996,
%U A017961 322687697779,1406563064942,6131066257801,26724698233906
%N A017961 Powers of sqrt(19) rounded down.
%H A017961 Vincenzo Librandi, <a href="/A017961/b017961.txt">Table of n, a(n) for n = 0..700</a>
%F A017961 a(n) = floor(sqrt(19^n)). - _Vincenzo Librandi_, Jun 24 2011
%t A017961 Table[Floor[(Sqrt[19])^n],{n,0,30}] (* _Harvey P. Dale_, May 22 2014 *)
%o A017961 (Magma) [Floor(Sqrt(19^n)): n in [0..30]]; // _Vincenzo Librandi_, Jun 24 2011
%o A017961 (PARI) a(n)=sqrtint(19^n) \\ _Charles R Greathouse IV_, Nov 18 2011
%Y A017961 Cf. A010475 (sqrt(19)).
%K A017961 nonn
%O A017961 0,2
%A A017961 _N. J. A. Sloane_