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
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Feb 09 2010
EXTENSIONS
Corrected and extended by Harvey P. Dale, Apr 11 2011
STATUS
approved