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 A081300 #6 Sep 08 2022 08:45:09
%S A081300 1,5,55,481,10501,117181,3879331,52751105,2351234953,37766866501,
%T A081300 2120129149711,39311679607201,2663716583547085,56019878838007085,
%U A081300 4448878347069812251,104660471059169187841,9534251497305019644433
%N A081300 Diagonal of square array A081297.
%H A081300 Vincenzo Librandi, <a href="/A081300/b081300.txt">Table of n, a(n) for n = 0..200</a>
%F A081300 a(n) = ((n+1)^(n+3)-(-n)^(n+3))/(2*n+1).
%t A081300 Table[((n + 1)^(n + 3) - (-n)^(n + 3)) / (2 n + 1), {n, 0, 20}] (* _Vincenzo Librandi_, Aug 07 2013 *)
%o A081300 (Magma) [((n+1)^(n+3)-(-n)^(n+3))/(2*n+1): n in [0..20]]; // _Vincenzo Librandi_, Aug 07 2013
%Y A081300 Cf. A081298, A081299, A081301, A081302.
%K A081300 easy,nonn
%O A081300 0,2
%A A081300 _Paul Barry_, Mar 17 2003