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 A020925 #30 Mar 25 2022 09:14:01
%S A020925 1,-26,286,-1716,6006,-12012,12012,-3432,-858,-572,-572,-728,-1092,
%T A020925 -1848,-3432,-6864,-14586,-32604,-76076,-184184,-460460,-1184040,
%U A020925 -3121560,-8414640,-23140260,-64792728,-184410072,-532740208,-1560167752,-4626704368,-13880113104
%N A020925 Expansion of (1-4*x)^(13/2).
%H A020925 Robert Israel, <a href="/A020925/b020925.txt">Table of n, a(n) for n = 0..1694</a>
%F A020925 a(n) = (-2)^n * Product_{i=0..n-1} (13-2*i) / n! for n>0. - _R. J. Mathar_, Feb 19 2008
%F A020925 D-finite with recurrence: n*a(n) - 2*(2*n-13)*a(n-1) = 0 for n>0. - _Bruno Berselli_, Jul 02 2018
%F A020925 a(n) ~ -135135 * 2^(2*n - 7) / (sqrt(Pi) * n^(15/2)). - _Vaclav Kotesovec_, Jul 02 2018
%F A020925 From _Amiram Eldar_, Mar 25 2022: (Start)
%F A020925 a(n) = (-4)^n*binomial(13/2, n).
%F A020925 Sum_{n>=0} 1/a(n) = 960/1001 - 10*Pi/(3^8*sqrt(3)).
%F A020925 Sum_{n>=0} (-1)^n/a(n) = 244659776/234609375 - 12*log(phi)/(5^7*sqrt(5)), where phi is the golden ratio (A001622). (End)
%p A020925 f := k -> -135135*(2*k)!/((2*k-1)*(2*k-3)*(2*k-5)*(2*k-7)*(2*k-9)*(2*k-11)*(-13+2*k)*(k!)^2):
%p A020925 map(f, [$0..30]); # _Robert Israel_, Jul 02 2018
%t A020925 CoefficientList[Series[(1-4*x)^(13/2), {x, 0, 50}], x] (* _Amiram Eldar_, Mar 25 2022 *)
%o A020925 (PARI) my(x = 'x + O('x^40)); Vec((1-4*x)^(13/2)) \\ _Michel Marcus_, Jul 02 2018
%Y A020925 Cf. A001622, A002420, A002421, A002422, A002423, A002424, A020923.
%K A020925 sign
%O A020925 0,2
%A A020925 _N. J. A. Sloane_