OFFSET
0,5
COMMENTS
Shifts 3 places left when e.g.f. is squared.
LINKS
Georg Fischer, Table of n, a(n) for n = 0..500
FORMULA
E.g.f. A(x) satisfies: A(x) = 1 + x + x^2/2 + Integral( Integral( Integral A(x)^2 dx) dx) dx.
MATHEMATICA
a[0] = a[1] = a[2] = 1; a[n_] := a[n] = Sum[Binomial[n - 3, k] a[k] a[n - k - 3], {k, 0, n - 3}]; Table[a[n], {n, 0, 28}]
nmax = 28; A[_] = 0; Do[A[x_] = 1 + x + x^2/2 + Integrate[Integrate[Integrate[A[x]^2, x], x], x] + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x] Range[0, nmax]!
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Jul 04 2020
STATUS
approved