Search: id:A024670
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%I A024670
%S A024670 9,28,35,65,72,91,126,133,152,189,217,224,243,280,341,344,351,370,407,
               468,
%T A024670 513,520,539,559,576,637,728,730,737,756,793,854,855,945,1001,1008,1027,
%U A024670 1064,1072,1125,1216,1241,1332,1339,1343,1358,1395,1456,1512,1547,1674
%N A024670 Numbers that are distinct sums of cubes of 2 distinct positive integers.
%C A024670 This sequence contains no primes since x^3+y^3=(x^2-xy+y^2)(x+y). - M. 
               F. Hasler (www.univ-ag.fr/~mhasler), Apr 12 2008
%H A024670 M. F. Hasler, <a href="b024670.txt">Table of n, a(n) for n=1,...,902</
               a>.
%H A024670 <a href="Sindx_Su.html#ssq">Index to sequences related to sums of cubes</
               a>
%t A024670 lst={};Do[Do[x=a^3;Do[y=b^3;If[x+y==n,AppendTo[lst,n]],{b,Floor[(n-x)^(1/
               3)],a+1,-1}],{a,Floor[n^(1/3)],1,-1}],{n,6!}];lst [From Vladimir 
               Orlovsky (4vladimir(AT)gmail.com), Jan 22 2009]
%o A024670 (PARI) isA024670(n)=for( i=ceil(sqrtn( n\2+1,3)),sqrtn(n-.5,3), isA000578(n-i^3) 
               & return(1)) /* One could also use "for( i=2,sqrtn( n\2-1,3),...)" 
               but this is much slower since there are less cubes in [n/2,n] than 
               in [1,n/2]. Replacing the -1 here by +.5 would yield A003325, allowing 
               for a(n)=x^3+x^3. Replacing -1 by 0 may miss some a(n) of this form 
               due to rounding errors. */ - M. F. Hasler (www.univ-ag.fr/~mhasler), 
               Apr 12 2008
%Y A024670 See also: Sums of 2 positive cubes (not necessarily distinct): A003325. 
               Sums of 3 distinct positive cubes: A024975. Sums of distinct positive 
               cubes: A003997. Sums of 2 distinct nonnegative cubes: A114090. Sums 
               of 2 nonnegative cubes: A004999. Sums of 2 distinct positive squares: 
               A004431. Cubes: A000578.
%Y A024670 Sequence in context: A044999 A155473 A127629 this_sequence A141805 A124360 
               A041152
%Y A024670 Adjacent sequences: A024667 A024668 A024669 this_sequence A024671 A024672 
               A024673
%K A024670 nonn
%O A024670 1,1
%A A024670 Clark Kimberling (ck6(AT)evansville.edu)

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