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A173106
Partial sums of A005100.
3
1, 3, 6, 10, 15, 22, 30, 39, 49, 60, 73, 87, 102, 118, 135, 154, 175, 197, 220, 245, 271, 298, 327, 358, 390, 423, 457, 492, 529, 567, 606, 647, 690, 734, 779, 825, 872, 921, 971, 1022, 1074, 1127, 1182, 1239, 1297, 1356, 1417, 1479, 1542, 1606, 1671, 1738, 1806, 1875, 1946
OFFSET
1,2
LINKS
FORMULA
a(n) = Sum_{i=1..n} A005100(i).
a(n) ~ c * n^2, where c = 1/(2*A318172) = 0.66455... - Amiram Eldar, Oct 21 2020
MATHEMATICA
Accumulate[Select[Range[100], DivisorSigma[1, #]<2#&]] (* Harvey P. Dale, Apr 11 2011 *)
PROG
(GAP) D:=Filtered([1..80], n->Sigma(n)<2*n);;
a:=List([1..Length(D)], i->Sum([1..i], j->D[j])); # Muniru A Asiru, Jun 08 2018
(PARI) lista(nn) = {my(s = 0); for (n=1, nn, if (sigma(n) < 2*n, s += n; print1(s, ", ")); ); } \\ Michel Marcus, Jun 09 2018
CROSSREFS
Sequence in context: A109442 A360954 A025723 * A022784 A025736 A288425
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Feb 09 2010
EXTENSIONS
Corrected and extended by Harvey P. Dale, Apr 11 2011
STATUS
approved