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 A061798 Number of sums i^3 + j^3 that occur more than once for 1<=i<=j<=n. 2
 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, 7, 8, 8, 8, 9, 10, 10, 10, 10, 10, 10, 10, 10, 12, 12, 12, 13, 13, 14, 15, 16, 16, 16, 17, 17, 19, 19, 19, 19, 20, 20, 20, 21, 23, 24, 24, 24, 25, 25, 25, 25 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,16 LINKS Seiichi Manyama, Table of n, a(n) for n = 1..1000 PROG (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 (Ruby) def A(n) h = {} (1..n).each{|i| (i..n).each{|j| k = i * i * i + j * j * j if h.has_key?(k) h[k] += 1 else h[k] = 1 end } } h.to_a.select{|i| i[1] > 1}.size end def A061798(n) (1..n).map{|i| A(i)} end p A061798(80) # Seiichi Manyama, May 14 2024 CROSSREFS Cf. A000217, A011541, A061791. Sequence in context: A105390 A347941 A013941 * A345206 A318585 A029241 Adjacent sequences: A061795 A061796 A061797 * A061799 A061800 A061801 KEYWORD nonn,changed AUTHOR Labos Elemer, Jun 22 2001 STATUS approved

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Last modified May 23 16:36 EDT 2024. Contains 372765 sequences. (Running on oeis4.)