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Numbers that are the sum of 6 positive cubes.
45

%I #34 Oct 21 2023 21:40:58

%S 6,13,20,27,32,34,39,41,46,48,53,58,60,65,67,69,72,76,79,83,84,86,90,

%T 91,95,97,98,102,104,105,109,110,116,117,121,123,124,128,130,132,135,

%U 136,137,139,142,143,144,146,147,151,153,154,156,158,160,161,162,163,165,170

%N Numbers that are the sum of 6 positive cubes.

%C As the order of addition doesn't matter we can assume terms are in increasing order. - _David A. Corneth_, Aug 01 2020

%H David A. Corneth, <a href="/A003329/b003329.txt">Table of n, a(n) for n = 1..10000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/CubicNumber.html">Cubic Number</a>.

%e From _David A. Corneth_, Aug 01 2020: (Start)

%e 1647 is in the sequence as 1647 = 3^3 + 3^3 + 5^3 + 5^3 + 7^3 + 10^3.

%e 3319 is in the sequence as 3319 = 5^3 + 5^3 + 5^3 + 6^3 + 10^3 + 12^3.

%e 4038 is in the sequence as 4038 = 3^3 + 3^3 + 6^3 + 8^3 + 8^3 + 14^3. (End)

%t max = 200; cmax = Ceiling[(max - 5)^(1/3)]; cc = Array[c, 6]; iter = Sequence @@ Transpose[ {cc, Join[{1}, Most[cc]], Table[cmax, {6}]}]; Union[ Reap[ Do[ a = Total[cc^3]; If[a <= max, Sow[a]], Evaluate[iter]]][[2, 1]]] (* _Jean-François Alcover_, Oct 23 2012 *)

%o (PARI) (A003329_upto(N,k=6,m=3)=[i|i<-[1..#N=sum(n=1,sqrtnint(N,m), 'x^n^m, O('x^N))^k], polcoef(N,i)])(200) \\ _M. F. Hasler_, Aug 02 2020

%o (Python)

%o from collections import Counter

%o from itertools import combinations_with_replacement as multi_combs

%o def aupto(lim):

%o c = filter(lambda x: x<=lim, (i**3 for i in range(1, int(lim**(1/3))+2)))

%o s = filter(lambda x: x<=lim, (sum(mc) for mc in multi_combs(c, 6)))

%o counts = Counter(s)

%o return sorted(k for k in counts)

%o print(aupto(170)) # _Michael S. Branicky_, Jun 13 2021

%Y Cf. A048929, A048930, A048931.

%Y Cf. A057907 (Complement)

%Y Cf. A###### (x, y) = Numbers that are the sum of x nonzero y-th powers:

%Y A000404 (2, 2), A000408 (3, 2), A000414 (4, 2), A047700 (5, 2),

%Y A003325 (2, 3), A003072 (3, 3), A003327 .. A003335 (4 .. 12, 3),

%Y A003336 .. A003346 (2 .. 12, 4), A003347 .. A003357 (2 .. 12, 5),

%Y A003358 .. A003368 (2 .. 12, 6), A003369 .. A003379 (2 .. 12, 7),

%Y A003380 .. A003390 (2 .. 12, 8), A003391 .. A004801 (2 .. 12, 9),

%Y A004802 .. A004812 (2 .. 12, 10), A004813 .. A004823 (2 .. 12, 11).

%K nonn,easy

%O 1,1

%A _N. J. A. Sloane_

%E More terms from _Eric W. Weisstein_