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Natural numbers of the form p^3 - q^3, where p and q are primes.
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%I #17 Mar 15 2023 11:12:20

%S 19,98,117,218,316,335,866,988,1206,1304,1323,1854,1946,2072,2170,

%T 2189,2716,3582,4570,4662,4788,4886,4905,5308,5402,5528,6516,6734,

%U 6832,6851,7254,9970,10586,10836,11824,12042,12140,12159,12222,17530,17624,18268

%N Natural numbers of the form p^3 - q^3, where p and q are primes.

%C To find all differences p^3 - q^3 less than N, it is required that all primes p and q up to sqrt(N/6) be tested.

%H T. D. Noe, <a href="/A086120/b086120.txt">Table of n, a(n) for n=1..10000</a>

%e 117 belongs to the sequence because it can be written as 5^3 - 2^3.

%t sumList[x_List, y_List] := (punchline = {}; Do[punchline = Union[punchline, x[[i]] + y], {i, Length[x]}]; punchline); posPart[x_List] := (punchline = {}; Do[If[x[[i]] > 0, punchline = Union[punchline, {x[[i]]}]], {i, Length[x]}]; punchline); posPart[sumList[Prime[Range[10]]^3, - Prime[Range[10]]^3]]

%t nn=10^5; Union[Reap[Do[n=Prime[i]^3-Prime[j]^3; If[n<=nn, Sow[n]], {i,PrimePi[Sqrt[nn/6]]}, {j,i-1}]][[2,1]]] (* _T. D. Noe_, Oct 04 2010 *)

%t With[{upto=20000},Select[Abs[#[[1]]-#[[2]]]&/@Subsets[Prime[ Range[ Sqrt[ upto/6]]]^3,{2}]//Union,#<=upto&]] (* _Harvey P. Dale_, Dec 10 2017 *)

%Y Cf. A086119, A086121. Also see A045636, A045699.

%K nonn

%O 1,1

%A _Hollie L. Buchanan II_, Jul 11 2003

%E Corrected by _T. D. Noe_, Oct 04 2010