OFFSET
0,2
COMMENTS
More generally, "least integer coefficients of A(x), where 1<=a(n)<=m, such that A(x)^(1/m) consists entirely of integer coefficients", appears to have a unique solution for all m>0. Is this sequence periodic?
LINKS
Robert G. Wilson v, Table of n, a(n) for n = 0..5000.
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.
MATHEMATICA
a[0] = 1; a[n_] :=a[n] = Block[{k=1, s = Sum[a[i]*x^i, {i, 0, n-1}]}, While[ Union[ IntegerQ /@ CoefficientList[ Series[(s+k*x^n)^(1/4), {x, 0, n}], x]] != {True}, k++ ]; k]; Table[ a[n], {n, 0, 104}] (* Robert G. Wilson v *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, May 09 2003
EXTENSIONS
More terms from Robert G. Wilson v, Jul 26 2005
STATUS
approved