OFFSET
0,4
COMMENTS
Limit a(n)/a(n+1) -> r = -0.269562488839799 where A(r)=0.
LINKS
Robert Israel, Table of n, a(n) for n = 0..1000
N. Heninger, E. M. Rains and N. J. A. Sloane, On the Integrality of n-th Roots of Generating Functions, arXiv:math/0509316 [math.NT], 2005-2006.
N. Heninger, E. M. Rains and N. J. A. Sloane, On the Integrality of n-th Roots of Generating Functions, J. Combinatorial Theory, Series A, 113 (2006), 1732-1745.
MAPLE
g:= 1: a[0]:= 1:
for n from 1 to 50 do
a[n]:= -floor((coeff(g^4, x, n)-1)/4);
g:= g + a[n]*x^n;
od:
seq(a[n], n=0..50); # Robert Israel, Sep 04 2019
MATHEMATICA
kmax = 30;
A[x_] = Sum[a[k] x^k, {k, 0, kmax}];
coes = CoefficientList[A[x]^4 + O[x]^(kmax + 1), x];
r = {a[0] -> 1, a[1] -> 1}; coes = coes /. r;
Do[r = Flatten @ Append[r, Reduce[1 <= coes[[k]] <= 4, a[k-1], Integers] // ToRules];
coes = coes /. r, {k, 3, kmax + 1}];
Table[a[k], {k, 0, kmax}] /. r (* Jean-François Alcover, Jul 26 2018 *)
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, May 20 2003
STATUS
approved