A001239 Numbers that are the sum of 3 nonnegative cubes in more than 1 way.
216, 251, 344, 729, 855, 1009, 1072, 1366, 1457, 1459, 1520, 1674, 1728, 1729, 1730, 1737, 1756, 1763, 1793, 1854, 1945, 2008, 2072, 2241, 2414, 2456, 2458, 2729, 2736, 2752, 3060, 3391, 3402, 3457, 3500, 3592, 3599, 3655, 3744, 3745
Offset: 1
Keywords
References
- G. H. Hardy, Ramanujan, Cambridge Univ. Press, 1940, p. 12.
- David Wells, The Penguin Dictionary of Curious and Interesting Numbers, Penguin Books, NY, 1986, p. 165.
Links
- Christian N. K. Anderson, Table of n, a(n) for n = 1..10000
- Christian N. K. Anderson, Decomposition of first 10000 terms into cube triples
Programs
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Mathematica
Select[Range[4000], Length[PowersRepresentations[#, 3, 3]] > 1 &] (* Harvey P. Dale, Feb 03 2011 *)
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PARI
is(n)=my(t); for(a=0, sqrtnint(n, 3), my(a3=a^3, c); for(b=0, min(a, sqrtnint(n-a3, 3)), if(ispower(n-a3-b^3, 3, &c) && c <= b && t++>1, return(1)))); 0 \\ Charles R Greathouse IV, Jul 02 2017