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A180089
Semiprimes which are the sum of three distinct positive cubes in two or more distinct ways.
3
1366, 1457, 1793, 1945, 3599, 4105, 5435, 7379, 8315, 9017, 10261, 10963, 11773, 12706, 13957, 15163, 15371, 15553, 15751, 15758, 16271, 17263, 17354, 17947, 18649, 19027, 19369, 19657, 19729, 19774, 19781, 19907, 21026, 21167, 22411
OFFSET
1,1
COMMENTS
2^3+3^3+11^3=5^3+8^3+9^3=1366=2*683, 1^3+5^3+11^3=6^3+8^3+9^3=1457=31*47,..
MATHEMATICA
f[n_]:=Last/@FactorInteger[n]=={1, 1}; lst={}; Do[Do[Do[If[f[p=a^3+b^3+c^3], AppendTo[lst, p]], {c, b-1, 1, -1}], {b, a-1, 1, -1}], {a, 55}]; lst1=Sort@lst; lst={}; Do[If[lst1[[n]]==lst1[[n+1]], AppendTo[lst, lst1[[n]]]], {n, Length[lst1]-1}]; lst
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved