A038593 Differences between positive cubes in 1, 2 or 3 ways: union of A014439, A014440 and A014441.
7, 19, 26, 37, 56, 61, 63, 91, 98, 117, 124, 127, 152, 169, 189, 208, 215, 217, 218, 271, 279, 296, 316, 331, 335, 342, 386, 387, 397, 448, 469, 485, 488, 504, 511, 513, 547, 602, 604, 631, 657, 665, 702, 721, 728, 784, 817, 819, 866, 875, 919, 936, 973, 988
Offset: 1
Keywords
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Programs
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Maple
N:= 1000: # to get all terms <= N X:= floor(sqrt(N/3)): V:= Vector(N): for x from 2 to X do if x^3 > N then y0:= iroot(x^3-N,3); if x^3 - y0^3 > N then y0:= y0+1 fi; else y0:= 1 fi; for y from y0 to x-1 do V[x^3 - y^3] := V[x^3 - y^3]+1 od od: select(t -> V[t] <= 3 and V[t]>=1, [$1..N]); # Robert Israel, Dec 10 2015 -
Mathematica
r = 988; p = 3; Sort@Drop[Flatten@Select[Tally@Reap[Do[n = i^p - j^p; If[n <= r, Sow[n]], {i, Ceiling[(r/p)^(1/(p - 1))]}, {j, i}]][[2, 1]], 0 < #[[2]] < 4 &], {2, -1, 2}] (* Arkadiusz Wesolowski, Dec 10 2015 *)
Extensions
Corrected by Don Reble, Nov 19 2006
Comments