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 A157280 #10 Jun 02 2025 01:24:36
%S A157280 1,52,43833,149670844,1346634725665,25571928251231076,
%T A157280 893591647147188285577,52327970757667659912764908,
%U A157280 4796836032234830356783078467969
%N A157280 a(n) arises in the normal ordering of n-th power of the operator (d/dx)(x(d/dx))^4.
%C A157280 this sequence generates the fifth terms of the following sequences:
%C A157280 a(2)=52=A000110(5), a(3)=43833=A020556(5), a(4)=149670844=A069223(5),
%C A157280 a(5)=1346634725665=A071379(5),a(6)=25571928251231076=A070227(5)
%F A157280 Sequence defined through the following hypergeometric-type generating function, in Maple notation:
%F A157280 exp(-1)*sum(hypergeom([k+1,k+1,k+1,k+1],[1,1,1,1],x)/k!,k=0..infinity)=sum(a(n)*x^n/(n!)^5,n=0..infinity),
%F A157280 which is itself an infinite sum of hypergeometric functions.
%t A157280 nMax = 8; kMax = 50; seq0 = {}; seq = {1}; While[seq != seq0, seq0 = seq; seq = (1/E Sum[HypergeometricPFQ[{k+1, k+1, k+1, k+1}, {1, 1, 1, 1}, x]/k!, {k, 0, kMax}] + O[x]^(nMax+1) // CoefficientList[#, x]&) Range[0, nMax]!^5 // Round; kMax += 10; Print[kMax]]; A157280 = seq (* _Jean-François Alcover_, Nov 07 2016 *)
%K A157280 nonn
%O A157280 1,2
%A A157280 _Karol A. Penson_, Feb 26 2009