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%I #25 Aug 03 2020 08:52:10
%S 2,129,256,2188,2315,4374,16385,16512,18571,32768,78126,78253,80312,
%T 94509,156250,279937,280064,282123,296320,358061,559872,823544,823671,
%U 825730,839927,901668,1103479,1647086,2097153,2097280,2099339,2113536
%N Numbers that are the sum of 2 positive 7th powers.
%H Robert Israel, <a href="/A003369/b003369.txt">Table of n, a(n) for n = 1..10000</a>
%e From _David A. Corneth_, Aug 03 2020: (Start)
%e 3909794986386 is in the sequence as 3909794986386 = 57^7 + 57^7.
%e 6061605477062 is in the sequence as 6061605477062 = 19^7 + 67^7.
%e 26019535290982 is in the sequence as 26019535290982 = 61^7 + 81^7. (End)
%p N:= 10^7: # to get all terms <= N
%p S:= select(`<=`, {seq(seq(a^7+b^7, a=1..b), b=1..floor(N^(1/7)))}, N):
%p sort(convert(S, list)); # _Robert Israel_, Sep 03 2017
%t lst={}; Do[If[(a^7+b^7)==n, AppendTo[lst, n]], {n, 200000}, {a, (n/2)^(1/7)}, {b, a, (n-a^7)^(1/7)}]; lst (* _XU Pingya_, Sep 03 2017 *)
%t Module[{upto=10},Select[Union[Total/@Tuples[Range[upto]^7,2]],#<= (upto^7)&]] (* _Harvey P. Dale_, Feb 04 2019 *)
%Y Cf. A000404 (2 squares), A003325 (2 cubes), A003336 (2 4th), A003347 (2 5th), A003358 (2 6th), A088719 (2 distinct 7th), A003380 (2 8th).
%Y Cf. A001015 (seventh powers).
%K nonn,easy
%O 1,1
%A _N. J. A. Sloane_
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