OFFSET
1,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..10000
MAPLE
b:= proc(n, i, t) option remember; n=0 or i>0 and t>0
and (b(n, i-1, t) or i^9<=n and b(n-i^9, i, t-1))
end:
a:= proc(n) option remember; local k;
for k from 1+ `if`(n=1, -1, a(n-1))
while not b(k, iroot(k, 9), 9) do od; k
end:
seq(a(n), n=1..60); # Alois P. Heinz, Sep 16 2016
MATHEMATICA
b[n_, k_, i_, t_] := b[n, k, i, t] = n == 0 || i > 0 && t > 0 && (b[n, k, i - 1, t] || i^k <= n && b[n - i^k, k, i, t - 1]);
A[n_, k_] := A[n, k] = Module[{m}, For[m = 1 + If[n == 1, -1, A[n - 1, k]], !b[m, k, m^(1/k) // Floor, k], m++]; m];
a[n_] := A[n, 9];
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Alois P. Heinz, Sep 16 2016
STATUS
approved