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%I #22 Nov 12 2020 06:37:22
%S 1,3,6,10,15,22,30,39,49,60,73,87,102,118,135,154,175,197,220,245,271,
%T 298,327,358,390,423,457,492,529,567,606,647,690,734,779,825,872,921,
%U 971,1022,1074,1127,1182,1239,1297,1356,1417,1479,1542,1606,1671,1738,1806,1875,1946
%N Partial sums of A005100.
%H Muniru A Asiru, <a href="/A173106/b173106.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = Sum_{i=1..n} A005100(i).
%F a(n) ~ c * n^2, where c = 1/(2*A318172) = 0.66455... - _Amiram Eldar_, Oct 21 2020
%t Accumulate[Select[Range[100],DivisorSigma[1,#]<2#&]] (* _Harvey P. Dale_, Apr 11 2011 *)
%o (GAP) D:=Filtered([1..80], n->Sigma(n)<2*n);;
%o a:=List([1..Length(D)],i->Sum([1..i],j->D[j])); # _Muniru A Asiru_, Jun 08 2018
%o (PARI) lista(nn) = {my(s = 0); for (n=1, nn, if (sigma(n) < 2*n, s += n; print1(s, ", ")););} \\ _Michel Marcus_, Jun 09 2018
%Y Cf. A005100, A318172.
%K easy,nonn
%O 1,2
%A _Jonathan Vos Post_, Feb 09 2010
%E Corrected and extended by _Harvey P. Dale_, Apr 11 2011
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