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 A081299 #6 Sep 08 2022 08:45:09
%S A081299 1,3,13,181,1281,32551,314245,11638089,141943681,6914792611,
%T A081299 101829922701,6152865979261,106138316846017,7657555132292703,
%U A081299 151395000617362741,12699162274678909201,283052059672669084161
%N A081299 Diagonal of square array A081297.
%H A081299 Vincenzo Librandi, <a href="/A081299/b081299.txt">Table of n, a(n) for n = 0..200</a>
%F A081299 a(n) = ((n+1)^(n+2)-(-n)^(n+2))/(2*n+1).
%t A081299 Table[((n + 1)^(n + 2) - (-n)^(n + 2)) / (2 n + 1), {n, 0, 20}] (* _Vincenzo Librandi_, Aug 08 2013 *)
%o A081299 (Magma) [((n+1)^(n+2)-(-n)^(n+2))/(2*n+1): n in [0..20]]; // _Vincenzo Librandi_, Aug 08 2013
%Y A081299 Cf. A081298, A081300, A081301, A081302.
%K A081299 easy,nonn
%O A081299 0,2
%A A081299 _Paul Barry_, Mar 17 2003