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 A260122 #31 Feb 16 2025 08:33:26
%S A260122 1,2,10,166,9295,2007754,1822022612,7463004618900,146894319913813741,
%T A260122 14689431991381374106820,7846297508164921345697431897,
%U A260122 23428918818620324499511000487089219,407740674993626332726840969430118771134776
%N A260122 a(n) = floor( Product_{k = 1..n} k^(k/2) ).
%H A260122 G. C. Greubel, <a href="/A260122/b260122.txt">Table of n, a(n) for n = 1..50</a>
%H A260122 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Hyperfactorial.html">Hyperfactorial</a>
%F A260122 a(n) = floor(sqrt(A002109(n))) = A000196(A002109(n)).
%F A260122 a(n) ~ sqrt(A)*n^(n*(n+1)/4+1/24)/exp(n^2/8), where A is the Glaisher-Kinkelin constant (A074962). - _Ilya Gutkovskiy_, Dec 27 2016
%t A260122 Table[Floor[Sqrt[Hyperfactorial[n]]], {n, 1, 12}]
%o A260122 (PARI) a(n) = sqrtint(prod(k=2,n,k^k)) \\ _Charles R Greathouse IV_, Jul 17 2015
%Y A260122 Cf. A002109, A074962.
%K A260122 nonn
%O A260122 1,2
%A A260122 _Ilya Gutkovskiy_, Jul 17 2015