A003998 Numbers that are a sum of distinct positive cubes in more than one way.

216, 217, 224, 225, 540, 559, 560, 567, 568, 728, 729, 736, 737, 756, 757, 764, 793, 801, 820, 828, 854, 855, 862, 863, 881, 882, 889, 890, 918, 919, 926, 927, 945, 946, 953, 954, 980, 981, 1008, 1009, 1036, 1044, 1045, 1071, 1072, 1073, 1079, 1080

Offset

1,1

Links

Zak Seidov and Robert Israel, Table of n, a(n) for n = 1..10000 (n = 1..1038 from Zak Seidov)

Maple

F:= proc(x, y) option remember;
  if y = 0 then 1
  elif y < x^3 then 0
  elif y = x^3 then 1
  else procname(x+1, y) + procname(x+1, y-x^3)
  fi
end proc:
select(t -> F(1, t) > 1, [$1..10000]); # Robert Israel, Dec 31 2015

Mathematica

ok[n_] := Length[ Select[ Union[ Union /@ Flatten[ Table[ DeleteCases[ PowersRepresentations[n, k, 3], 0, 2], {k, 1, Floor[(n-1)^(1/3)]}], 1]], Total[#^3] == n & , 2]] == 2; Reap[ Do[ If[ ok[n], Print[n]; Sow[n]], {n, 1, 1100}]][[2, 1]](* Jean-François Alcover, Feb 23 2012 *)

Crossrefs

Cf. A001239.

Sequence in context: A013546 A192073 A018863 * A335544 A230400 A001239

Adjacent sequences: A003995 A003996 A003997 * A003999 A004000 A004001

Keyword

nonn,easy,nice

Author

N. J. A. Sloane

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), Mar 20 2000

Status

approved