Search: id:A061794
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%I A061794
%S A061794 1,3,3,5,5,7,7,7,7,7,7,10,10,10,10,11,11,11,11,11,11,11,11,14,14,14,14,
%T A061794 14,14,14,14,14,14,14,14,17,17,17,17,17,17,17,17,17,17,17,17,19,19,19,
%U A061794 19,19,19,19,19,19,19,19,19,22,22,22,22,22,22,22,22,22,22,22,22,22,22
%N A061794 Number of distinct sums d(i) + d(j) for 1<=i<=j<=n, d(k) = A000005(k) 
               = number of divisors function.
%e A061794 If the {s+t} sums are generated by adding 2 terms of an S set consisting 
               of n different entries, then at least 1, at most n(n+1)/2=A000217(n) 
               distinct values can be obtained. The set of first n tau-values gives 
               results falling between these two extremes. E.g. n=10, A000005:{1,
               2,2,3,2,4,2,4,3,4...}; possible values of sum of 2:{2,3,4,5,6,7,8}, 
               thus a(10)=7.
%t A061794 f[x_] := DivisorSigma[0, x] t0=Table[Length[Union[Flatten[Table[f[u]+f[w], 
               {w, 1, m}, {u, 1, m}]]]], {m, 1, 75}]
%Y A061794 A000217, A000005.
%Y A061794 Sequence in context: A069902 A085779 A078936 this_sequence A088524 A129337 
               A133909
%Y A061794 Adjacent sequences: A061791 A061792 A061793 this_sequence A061795 A061796 
               A061797
%K A061794 nonn
%O A061794 1,2
%A A061794 Labos E. (labos(AT)ana.sote.hu), Jun 22 2001

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