OFFSET
1,4
FORMULA
Conjecture: a(n)=1 iff n is 1, a prime or the square of an odd prime.
MATHEMATICA
f[n_] := Module[{j = 1, a}, a[0] = 1; a[l_] := a[l] = Block[{k = 1, s = Sum[ a[i]*x^i, {i, 0, l - 1}]}, While[ IntegerQ[ Last[ CoefficientList[ Series[(s + k*x^l)^(1/n), {x, 0, l}], x]]] != True, k++ ]; k]; While[a[j] != 1, j++ ]; j]; Table[ f[n]/n, {n, 10}]
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
Paul D. Hanna and Robert G. Wilson v, Aug 20 2005
EXTENSIONS
a(30)-a(50) from Robert G. Wilson v, Oct 29 2007
a(51)-a(65) from Robert G. Wilson v, Jul 25 2008
STATUS
approved