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 A222621 #38 Sep 08 2022 08:46:04
%S A222621 1,81,15625,5764801,3486784401,3138428376721,3937376385699289,
%T A222621 6568408355712890625,14063084452067724991009,
%U A222621 37589973457545958193355601,122694327386105632949003612841,480250763996501976790165756943041,2220446049250313080847263336181640625
%N A222621 a(n) = (2n-1)^(2n).
%H A222621 Vincenzo Librandi, <a href="/A222621/b222621.txt">Table of n, a(n) for n = 1..190</a>
%F A222621 a(n) = A005408(n-1)^A005843(n). - _Michel Marcus_, Apr 14 2018
%F A222621 Sum_{n>=1} 1/a(n) = A338168. - _Amiram Eldar_, Nov 29 2020
%e A222621 1^2; 3^4; 5^6; 7^8 and so on.
%t A222621 Table[(2 n - 1)^(2 n), {n, 20}] (* _T. D. Noe_, Feb 26 2013 *)
%o A222621 (Magma) [(2*n - 1)^(2*n): n in [1..13]]; // _Vincenzo Librandi_, Feb 26 2013
%o A222621 (PARI) a(n)=(2*n-1)^(2*n) \\ _Charles R Greathouse IV_, Aug 20 2013
%Y A222621 Cf. A005408, A005843, A085535, A338168.
%K A222621 nonn,easy
%O A222621 1,2
%A A222621 _Dave Durgin_, Feb 26 2013