|
%I #36 Jul 31 2021 23:41:12
%S 251,1009,1366,1457,1459,1520,1730,1737,1756,1763,1793,1854,1945,2008,
%T 2072,2241,2414,2456,2458,2729,2736,3060,3391,3457,3592,3599,3655,
%U 3745,3926,4105,4112,4131,4168,4229,4320,4376,4402,4437,4447,4473,4528,4616
%N Numbers that are the sum of 3 positive cubes in exactly 2 ways.
%C Subset of A008917; A025397 gives examples of numbers which are in A008917 but not here. - _R. J. Mathar_, May 28 2008
%C A025456(a(n)) = 2. - _Reinhard Zumkeller_, Apr 23 2009
%C Superset of A024974 . - _Christian N. K. Anderson_, Apr 11 2013
%H Christian N. K. Anderson, <a href="/A025396/b025396.txt">Table of n, a(n) for n = 1..10000</a>
%H Christian N. K. Anderson, <a href="/A025396/a025396.txt">Decomposition</a> of the first 10000 terms into the sets of three cubes
%e a(1) = 251 = 1^3+5^3+5^3 = 2^3+3^3+6^3. - _Christian N. K. Anderson_, Apr 11 2013
%t Select[Range[5000], Length[DeleteCases[PowersRepresentations[#,3,3], _?(MemberQ[#,0]&)]] == 2&] (* _Harvey P. Dale_, Jan 18 2012 *)
%o (PARI) is(n)=k=ceil((n-2)^(1/3)); d=0; for(a=1,k,for(b=a,k,for(c=b,k,if(a^3+b^3+c^3==n,d++))));d
%o n=3;while(n<5000,if(is(n)==2,print1(n,", "));n++) \\ _Derek Orr_, Aug 27 2015
%Y Cf. A008917, A025322, A025395, A025397, A025404, A343708, A344192.
%K nonn
%O 1,1
%A _David W. Wilson_
|
