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A061798 Number of sums i^3 + j^3 that occur more than once for 1<=i<=j<=n.

%I A061798 #34 May 14 2024 06:04:30
%S A061798 0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,2,2,2,2,3,3,3,4,4,4,4,4,5,5,7,
%T A061798 7,8,8,8,9,10,10,10,10,10,10,10,10,12,12,12,13,13,14,15,16,16,16,17,
%U A061798 17,19,19,19,19,20,20,20,21,23,24,24,24,25,25,25,25
%N A061798 Number of sums i^3 + j^3 that occur more than once for 1<=i<=j<=n.
%H A061798 Seiichi Manyama, <a href="/A061798/b061798.txt">Table of n, a(n) for n = 1..1000</a>
%o A061798 (PARI) a(n) = my(v=vector(2*n^3, i, 0)); for(i=1, n, for(j=i, n, v[i^3+j^3]+=1)); sum(i=1, #v, v[i]>1); \\ _Seiichi Manyama_, May 14 2024
%o A061798 (Ruby)
%o A061798 def A(n)
%o A061798   h = {}
%o A061798   (1..n).each{|i|
%o A061798     (i..n).each{|j|
%o A061798       k = i * i * i + j * j * j
%o A061798       if h.has_key?(k)
%o A061798         h[k] += 1
%o A061798       else
%o A061798         h[k] = 1
%o A061798       end
%o A061798     }
%o A061798   }
%o A061798   h.to_a.select{|i| i[1] > 1}.size
%o A061798 end
%o A061798 def A061798(n)
%o A061798   (1..n).map{|i| A(i)}
%o A061798 end
%o A061798 p A061798(80) # _Seiichi Manyama_, May 14 2024
%Y A061798 Cf. A000217, A011541, A061791.
%K A061798 nonn
%O A061798 1,16
%A A061798 _Labos Elemer_, Jun 22 2001