A025396 Numbers that are the sum of 3 positive cubes in exactly 2 ways.

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, 4473, 4528, 4616, 4733, 4833

Offset

1,1

Comments

Subset of A008917; A025397 gives examples of numbers which are in A008917 but not here. - R. J. Mathar, May 28 2008

A025456(a(n)) = 2. - Reinhard Zumkeller, Apr 23 2009

Superset of A024974 . - Christian N. K. Anderson, Apr 11 2013

References

Elena Deza and Michel Marie Deza, Figurate numbers, World Scientific Publishing (2012), page 307.

Links

Christian N. K. Anderson, Table of n, a(n) for n = 1..10000

Christian N. K. Anderson, Decomposition of the first 10000 terms into the sets of three cubes

Example

a(1) = 251 = 1^3+5^3+5^3 = 2^3+3^3+6^3. - Christian N. K. Anderson, Apr 11 2013

Mathematica

Select[Range[5000], Length[DeleteCases[PowersRepresentations[#, 3, 3], _?(MemberQ[#, 0]&)]] == 2&] (* Harvey P. Dale, Jan 18 2012 *)

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)==2, print1(n, ", ")); n++) \\ Derek Orr, Aug 27 2015

Crossrefs

Cf. A008917, A025322, A025395, A025397, A025404, A343708, A344192.

Sequence in context: A228672 A339182 A008917 * A185941 A215607 A099734

Adjacent sequences: A025393 A025394 A025395 * A025397 A025398 A025399

Keyword

nonn

Author

David W. Wilson

Status

approved