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 A056981 #16 Feb 16 2025 08:32:43
%S A056981 1,1,1,1,25,49,441,1089,184041,511225,5909761,17631601,863948449,
%T A056981 2704312009,34493775625,111759833025,93990019574025,312541206957225,
%U A056981 4201942893536025,14258670483605625,780804795682244025
%N A056981 a(n) = A002596(n)^2.
%C A056981 Numerator of h^(2n) in the Kummer-Gauss series for the perimeter of an ellipse.
%H A056981 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Gauss-KummerSeries.html">Gauss-Kummer Series.</a>
%H A056981 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Ellipse.html">Ellipse.</a>
%t A056981 Numerator[Table[Binomial[1/2, n]^2, {n, 50}]] (* _Artur Jasinski_, Aug 30 2016 *)
%Y A056981 Cf. A002596, A056982.
%K A056981 nonn,frac
%O A056981 0,5
%A A056981 _Eric W. Weisstein_
%E A056981 New description from _N. J. A. Sloane_, Feb 18 2004