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 A316661 #22 Jul 29 2022 18:32:30
%S A316661 1,2,4,15,64,317,1728,10268,65536,445376,3200000,24172677,191102976,
%T A316661 1575167570,13492928512,119786923327,1099511627776,10412878353557,
%U A316661 101559956668416,1018460448140641,10485760000000000,110692335104026964,1196683881290399744
%N A316661 a(n) = ceiling(sqrt((2*n)^n)).
%C A316661 a(0)=1 relies on the algebraic identity 0^0 = 1 (à la Knuth).
%H A316661 D. E. Knuth, <a href="https://www.jstor.org/stable/2325085">Two Notes on Notation</a>, The American Mathematical Monthly, 99 (1992), 403-422.
%t A316661 Join[{1}, Table[Ceiling[Sqrt[(2 n)^n]], {n, 30}]] (* _Vincenzo Librandi_, Jul 10 2018 *)
%o A316661 (PARI) a(n) = ceil(sqrt((2*n)^n)); \\ _Michel Marcus_, Jul 10 2018
%o A316661 (Magma) [Ceiling(Sqrt((2*n)^n)): n in [0..25]]; // _Vincenzo Librandi_, Jul 10 2018
%o A316661 (Python)
%o A316661 from math import isqrt
%o A316661 def A316661(n): return 1+isqrt((n<<1)**n-1) # _Chai Wah Wu_, Jul 29 2022
%Y A316661 Cf. A242764.
%K A316661 nonn,easy
%O A316661 0,2
%A A316661 _Greg Huber_, Jul 09 2018