A025398 Numbers that are the sum of 3 positive cubes in 3 or more ways.

5104, 9729, 12104, 12221, 12384, 13896, 14175, 17604, 17928, 19034, 20691, 21412, 21888, 24480, 28792, 29457, 30528, 31221, 32850, 34497, 35216, 36288, 38259, 39339, 39376, 40041, 40060, 40097, 40832, 40851, 41033, 41040, 41364, 41966, 42056, 42687

Offset

1,1

Links

Donovan Johnson, Table of n, a(n) for n = 1..10000

Formula

A008917(n) < a(n) <= A025397(n). - Jonathan Sondow, Oct 24 2013

{n: A025456(n) >= 3}. - R. J. Mathar, Jun 15 2018

Example

a(1) = A230477(3) = 5104 = 1^3 + 12^3 + 15^3 = 2^3 + 10^3 + 16^3 = 9^3 + 10^3 + 15^3. - Jonathan Sondow, Oct 24 2013

Mathematica

Select[ Range[ 50000], 2 < Length @ Cases[ PowersRepresentations[#, 3, 3], {_?Positive, _?Positive, _?Positive}] &] (* adapted from Alcover's program for A008917 by Jonathan Sondow, Oct 24 2013 *)

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<50000, if(is(n)>=3, print1(n, ", ")); n++) \\ Derek Orr, Aug 27 2015

Crossrefs

Cf. A008917, A018787, A025331, A025397, A025402, A025407, A230477, A343968, A344239.

Sequence in context: A330730 A343081 A219329 * A025397 A025402 A025401

Adjacent sequences: A025395 A025396 A025397 * A025399 A025400 A025401

Keyword

nonn

Author

David W. Wilson

Status

approved