A003998 - OEIS

%I #33 Jan 01 2016 17:29:34

%S 216,217,224,225,540,559,560,567,568,728,729,736,737,756,757,764,793,

%T 801,820,828,854,855,862,863,881,882,889,890,918,919,926,927,945,946,

%U 953,954,980,981,1008,1009,1036,1044,1045,1071,1072,1073,1079,1080

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

%H Zak Seidov and Robert Israel, <a href="/A003998/b003998.txt">Table of n, a(n) for n = 1..10000</a> (n = 1..1038 from Zak Seidov)

%p F:= proc(x,y) option remember;

%p   if y = 0 then 1

%p   elif y < x^3 then 0

%p   elif y = x^3 then 1

%p   else procname(x+1,y) + procname(x+1,y-x^3)

%p   fi

%p end proc:

%p select(t -> F(1,t) > 1, [$1..10000]); # _Robert Israel_, Dec 31 2015

%t 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 *)

%Y Cf. A001239.

%K nonn,easy,nice

%O 1,1

%A _N. J. A. Sloane_

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