A173106 Partial sums of A005100.

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

Muniru A Asiru, Table of n, a(n) for n = 1..10000

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

Cf. A005100, A318172.

Sequence in context: A109442 A360954 A025723 * A022784 A025736 A288425

Adjacent sequences: A173103 A173104 A173105 * A173107 A173108 A173109

Keyword

easy,nonn

Author

Jonathan Vos Post, Feb 09 2010

Extensions

Corrected and extended by Harvey P. Dale, Apr 11 2011

Status

approved