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A025400 Numbers that are the sum of 3 distinct positive cubes in exactly 2 ways. 6

%I #16 Apr 26 2020 13:05:49

%S 1009,1366,1457,1520,1737,1756,1793,1854,1945,2072,2241,2456,2736,

%T 3060,3592,3599,3745,3926,4105,4131,4168,4229,4320,4376,4437,4447,

%U 4473,4616,4733,4922,5130,5435,5472,5643,5706,5825,5832,6183,6301,6642,6848,6904

%N Numbers that are the sum of 3 distinct positive cubes in exactly 2 ways.

%H Chai Wah Wu, <a href="/A025400/b025400.txt">Table of n, a(n) for n = 1..10000</a>

%F {n: A025469(n) = 2}. - _R. J. Mathar_, Jun 15 2018

%t Reap[ For[n = 1, n <= 7000, n++, pr = Select[ PowersRepresentations[n, 3, 3], Times @@ # != 0 && Length[#] == Length[Union[#]] &] ; If[pr != {} && Length[pr] == 2, Print[n, pr]; Sow[n]]]][[2, 1]] (* _Jean-François Alcover_, Jul 31 2013 *)

%t Module[{nn=20},Select[Tally[Total/@Subsets[Range[nn]^3,{3}]],#[[2]]==2 && #[[1]]<= nn^3-9&][[All,1]]]//Union (* _Harvey P. Dale_, Apr 26 2020 *)

%Y Cf. A025397 (not necessarily distinct)

%K nonn

%O 1,1

%A _David W. Wilson_

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Last modified March 19 01:57 EDT 2024. Contains 370952 sequences. (Running on oeis4.)