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A004893
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Numbers that are the sum of at most 9 positive 9th powers.
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2
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 512, 513, 514, 515, 516, 517, 518, 519, 520, 1024, 1025, 1026, 1027, 1028, 1029, 1030, 1031, 1536, 1537, 1538, 1539, 1540, 1541, 1542, 2048, 2049, 2050, 2051, 2052, 2053, 2560, 2561, 2562, 2563, 2564, 3072, 3073, 3074, 3075, 3584
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OFFSET
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1,3
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LINKS
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MAPLE
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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:
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MATHEMATICA
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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];
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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