A004881 Numbers that are the sum of at most 8 nonzero 8th powers.

0, 1, 2, 3, 4, 5, 6, 7, 8, 256, 257, 258, 259, 260, 261, 262, 263, 512, 513, 514, 515, 516, 517, 518, 768, 769, 770, 771, 772, 773, 1024, 1025, 1026, 1027, 1028, 1280, 1281, 1282, 1283, 1536, 1537, 1538, 1792, 1793, 2048, 6561, 6562, 6563, 6564, 6565, 6566

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..10000

Crossrefs

Column k=8 of A336820.

Programs

Maple

b:= proc(n, i, t) option remember; n=0 or i>0 and t>0
      and (b(n, i-1, t) or i^8<=n and b(n-i^8, 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, 8), 8) do od; k
    end:
seq(a(n), n=1..60);  # Alois P. Heinz, Sep 16 2016

Mathematica

b[n_, i_, t_] := b[n, i, t] = n == 0 || i > 0 && t > 0 && (b[n, i - 1, t] || i^8 <= n && b[n - i^8, i, t - 1]);
a[n_] := a[n] = (For[k = 1 + If[n == 1, -1, a[n - 1]], !b[k, k^(1/8) // Floor, 8], k++]; k);
Array[a, 60] (* Jean-François Alcover, Apr 06 2017, after Alois P. Heinz *)

Extensions

More terms from Alois P. Heinz, Sep 16 2016