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Search: id:A061791
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| A061791 |
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Number of distinct sums i^3 + j^3 for 1<=i<=j<=n. |
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+0
1
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| 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 77, 90, 104, 119, 134, 151, 169, 188, 208, 229, 251, 274, 297, 322, 348, 374, 402, 431, 461, 492, 523, 556, 588, 623, 658, 695, 733, 771, 810, 851, 893, 936, 980, 1025, 1071, 1118, 1164, 1213, 1263, 1313, 1365, 1417
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OFFSET
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1,2
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EXAMPLE
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If the {s+t} sums are generated by addition 2 terms of an S set consisting of n different entries, then at least 1, at most n(n+1)/2=A000217(n) distinct values can be obtained. The set of first n cubes gives results falling between these two extremes. E.g. S={1,8,27,...,2744,3375} provides 119 different sums of two, not necessarily different cubes:{2,9,....,6750}. Only a single sum occurs more than once: 1729(Ramanujan): 1729=1+1728=729+1000.
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MATHEMATICA
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f[x_] := x^3 t=Table[Length[Union[Flatten[Table[f[u]+f[w], {w, 1, m}, {u, 1, m}]]]], {m, 1, 75}]
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CROSSREFS
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A000217.
Sequence in context: A033443 A130490 A033444 this_sequence A105336 A130910 A105337
Adjacent sequences: A061788 A061789 A061790 this_sequence A061792 A061793 A061794
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Jun 22 2001
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