A008917 Numbers that are the sum of 3 positive cubes in more than one way.

251, 1009, 1366, 1457, 1459, 1520, 1730, 1737, 1756, 1763, 1793, 1854, 1945, 2008, 2072, 2241, 2414, 2456, 2458, 2729, 2736, 3060, 3391, 3457, 3592, 3599, 3655, 3745, 3926, 4105, 4112, 4131, 4168, 4229, 4320, 4376, 4402, 4437, 4447

Offset

1,1

Comments

Of course reordering the terms does not count.

A025456(a(n)) > 1. [Reinhard Zumkeller, Apr 23 2009]

Links

T. D. Noe and Christian N. K. Anderson, Table of n, a(n) for n = 1..10000 (first 1000 terms are from T. D. Noe)

Christian N. K. Anderson, Decomposition of first 10000 terms into multiple cube triples.

Example

a(2) = 1009 = 1^3+2^3+10^3 = 4^3+6^3+9^3.

Mathematica

Select[Range[4450], 1 < Length @ Cases[PowersRepresentations[#, 3, 3], {_?Positive, _?Positive, _?Positive}] &]  (* Jean-François Alcover, Apr 04 2011 *)

Prog

(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
n=3; while(n<5000, if(is(n)>1, print1(n, ", ")); n++) \\ Derek Orr, Aug 27 2015

Crossrefs

Cf. A001235, A003072, A024796, A025396, A025398, A025406, A309762.

Sequence in context: A108833 A228672 A339182 * A025396 A185941 A215607

Adjacent sequences: A008914 A008915 A008916 * A008918 A008919 A008920

Keyword

nonn,easy,nice

Author

N. J. A. Sloane and J. H. Conway

Status

approved