%I A061796
%S A061796 1,3,6,9,12,17,18,23,27,30,30,39,40,45,45,51,51,60,60,66,69,72,72,81,
%T A061796 81,81,86,92,94,103,103,112,112,114,114,131,133,133,133,141,141,151,
%U A061796 153,155,157,157,157,175,178,185,185,193,193,202,202,202,205,205,205
%N A061796 Number of distinct sums sigma(i) + sigma(j) for 1<=i<=j<=n, where sigma(k) 
               = A000203(k).
%e A061796 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 sigma-values 
               gives results falling between these two extremes.
%e A061796 E.g. n=10, A000203: {1,3,4,7,6,12,8,15,13,18...}. The 55 possible sigma(i)+sigma(j) 
               additions give 30 different results: {2,4,5,6,...,33,36}. Therefore 
               a(10)=30.
%t A061796 f[x_] := DivisorSigma[1, x] t0=Table[Length[Union[Flatten[Table[f[u]+f[w], 
               {w, 1, m}, {u, 1, m}]]]], {m, 1, 75}]
%Y A061796 Cf. A000217, A000203.
%Y A061796 Sequence in context: A084525 A130248 A072567 this_sequence A113241 A127621 
               A049707
%Y A061796 Adjacent sequences: A061793 A061794 A061795 this_sequence A061797 A061798 
               A061799
%K A061796 nonn
%O A061796 1,2
%A A061796 Labos E. (labos(AT)ana.sote.hu), Jun 22 2001