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 A383928 #20 May 18 2025 07:41:48 %S A383928 1,648,76896,4601088,194102784,6662320128,199818854400,5451206492160, %T A383928 138644854013952,3341194489757696,77151510667984896, %U A383928 1720777996555517952,37293854107184922624,788969931176505507840,16350749459194860011520,332885987884833366343680,6673058165121160335851520 %N A383928 Expansion of g.f. cosh(9*arctanh(4*sqrt(x))). %F A383928 a(n) = 4^n*(105 + 400*n + 3392*n^2 + 512*n^3 + 4096*n^4)*(2*n)!/(105*(n!)^2). %F A383928 O.g.f.: (1 + 576*x + 32256*x^2 + 344064*x^3 + 589824*x^4)/(-16*x + 1)^(9/2). %F A383928 E.g.f.: 134217728*((x^4 + 41/128*x^3 + 425/16384*x^2 + 525/1048576*x + 105/134217728)*BesselI(0, 8*x) + x*BesselI(1, 8*x)*(x^3 + 33/128*x^2 + 193/16384*x + 25/1048576))*exp(8*x)/105. %p A383928 seq(coeff(series((589824*x^4 + 344064*x^3 + 32256*x^2 + 576*x + 1)/(-16*x + 1)^(9/2), x, 17), x, k), k=0..16); %Y A383928 Cf. A285043, A285044, A285045, A285046. %K A383928 nonn,easy %O A383928 0,2 %A A383928 _Karol A. Penson_, May 15 2025