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A129965
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Triangular numbers that are the difference of nonnegative cubes.
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1
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0, 1, 91, 4095, 5886, 7875, 8128, 8911, 9045, 17955, 21736, 23653, 47278, 93961, 115921, 130816, 184528, 259560, 379756, 488566, 575128, 658378, 758296, 810901, 873181, 885115, 1060696, 1155960, 1358776, 1385280, 1997001, 2616328, 2685403
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OFFSET
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1,3
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LINKS
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EXAMPLE
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A000217(13) = Sum_{k=1..13} k = 91 = 216 - 125 = 6^3 - 5^3, so 91 is in the sequence. - Peter Munn, Dec 05 2022
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MAPLE
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M:= 10^7: # for terms <= M
S:= {0}:
for x from 1 while 3*x^2 - 3*x + 1 < M do
if x^3 < M then Y:= 0 else Y:= ceil(x^3-M) fi;
S:= S union select(t -> issqr(1+8*t), {seq(x^3 - y^3, y = Y .. x-1)});
od:
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MATHEMATICA
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With[{n = 5000}, Intersection[(#1*((#1 + 1)/2) & ) /@ Range[0, n], Flatten[Outer[ #1^3 - #2^3 &, Range[n], Range[0, n - 1]]]]]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Peter Pein (petsie(AT)dordos.net), Jun 13 2007, Jun 14 2007
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STATUS
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approved
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