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.
A054947[1] = 1; A054947[n_] := A054947[n] = 2^(n(n - 1)) - Sum[Binomial[n, j] 2^((n - 1)(n - j)) A054947[j], {j, 1, n - 1}]; A054948[0] = 1; A054948[n_] := A054948[n] = Module[{A}, A = 1 + Sum[ A054948[k]*x^k/k!, {k, 1, n - 1}]; n!*SeriesCoefficient[Sum[2^(k^2 - k)*x^k/k!/(A /. x -> 2^k*x) , {k, 0, n}], {x, 0, n}]]; a[n_] := (A054948[n] + A054947[n])/2; Array[a, 13] (* Jean-François Alcover, Aug 27 2019 *)
A054947[1] = 1; A054947[n_] := A054947[n] = 2^(n (n - 1)) - Sum[Binomial[n, j] 2^((n - 1) (n - j)) A054947[j], {j, 1, n - 1}]; A054948[0] = 1; A054948[n_] := A054948[n] = Module[{A}, A = 1 + Sum[ A054948[k]*x^k/k!, {k, 1, n - 1}]; n!*SeriesCoefficient[Sum[2^(k^2 - k)*x^k/k!/(A /. x -> 2^k*x) , {k, 0, n}], {x, 0, n}]]; a[n_] := (A054948[n] - A054947[n])/2; Array[a, 14] (* Jean-François Alcover, Aug 27 2019 *)
E.g.f.: A(x) = 1 + x + 5*x^2/2! + 429*x^3/3! + 399273*x^4/4! + 3072726201*x^5/5! +... where 1 = 1/A(x) + x/A(3*x) + 3^2*x^2/2!/A(3^2*x) + 3^6*x^3/3!/A(3^3*x) + 3^12*x^4/4!/A(3^4*x) + 3^20*x^5/5!/A(3^5*x) + 3^30*x^6/6!/A(3^6*x) +....
{a(n)=local(A=1+sum(k=1,n-1,a(k)*x^k/k!)+x*O(x^n));n!*polcoeff(sum(k=0,n,3^(k^2-k)*x^k/k!/subst(A,x,3^k*x)),n)}
for(n=0,15,print1(a(n),", "))
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