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 A065921 #19 Aug 17 2017 05:54:40
%S A065921 0,1,21,501,14455,496770,19911486,913839031,47303189361,2727741976785,
%T A065921 173455231572865,12060173714421756,910301022642409476,
%U A065921 74134150415555474881,6479678618270868170265,605042444997867941987385,60110944381660549838273911
%N A065921 Bessel polynomial {y_n}'(3).
%D A065921 J. Riordan, Combinatorial Identities, Wiley, 1968, p. 77.
%H A065921 G. C. Greubel, <a href="/A065921/b065921.txt">Table of n, a(n) for n = 0..345</a>
%H A065921 <a href="/index/Be#Bessel">Index entries for sequences related to Bessel functions or polynomials</a>
%F A065921 Recurrence: (n-1)^2*a(n) = (2*n - 1)*(3*n^2 - 3*n + 1)*a(n-1) + n^2*a(n-2). - _Vaclav Kotesovec_, Jul 22 2015
%F A065921 a(n) ~ 2^(n+1/2) * 3^(n-1) * n^(n+1) / exp(n-1/3). - _Vaclav Kotesovec_, Jul 22 2015
%F A065921 From _G. C. Greubel_, Aug 14 2017: (Start)
%F A065921 a(n) = 2*n*(1/2)_{n}*6^(n - 1)* hypergeometric1f1(1 - n, -2*n, 2/3).
%F A065921 E.g.f.: ((1 - 6*x)^(3/2) + 3*x*(1 - 6*x)^(1/2) + 15*x - 1) * exp((1 - sqrt(1 - 6*x))/3)/(9*(1 - 6*x)^(3/2)). (End)
%F A065921 G.f.: (t/(1-t)^3)*hypergeometric2f0(2,3/2; - ; 6*t/(1-t)^2). - _G. C. Greubel_, Aug 16 2017
%t A065921 Table[Sum[(n+k+1)!*3^k/((n-k-1)!*k!*2^(k+1)), {k,0,n-1}], {n,0,20}] (* _Vaclav Kotesovec_, Jul 22 2015 *)
%t A065921 Join[{0}, Table[2*n*Pochhammer[1/2, n]*6^(n - 1)* Hypergeometric1F1[1 - n, -2*n, 2/3], {n,1,50}]] (* _G. C. Greubel_, Aug 14 2017 *)
%o A065921 (PARI) for(n=0,50, print1(sum(k=0,n-1, (n+k+1)!*3^k/((n-k-1)!*k! *2^(k+1))), ", ")) \\ _G. C. Greubel_, Aug 14 2017
%Y A065921 Cf. A001514, A065920, A065922.
%K A065921 nonn
%O A065921 0,3
%A A065921 _N. J. A. Sloane_, Dec 08 2001