OFFSET
1,1
COMMENTS
Limit_{n->oo} a(n)/10^n = 0.752... is the density of deficient numbers (A005100).
MATHEMATICA
Accumulate@ Array[Count[Range[10^#, 10^(# + 1) - 1], _?(DivisorSigma[1, #] < 2 # &)] &, 6, 0] (* Michael De Vlieger, May 20 2018 *)
PROG
(GAP) P:=Filtered([1..10^7], n->Sigma(n)<2*n);;
o:=List([1..7], j->[]);; for i in [1..Length(P)] do for n in [1..Length(o)] do if P[i]<10^n then Add(o[n], P[i]); fi; od; od;
a:=List(o, Length);
(PARI) a(n) = sum(k=1, 10^n-1, sigma(k) < 2*k); \\ Michel Marcus, May 19 2018
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Muniru A Asiru, May 19 2018
EXTENSIONS
a(11)-a(17) from Hiroaki Yamanouchi, Aug 03 2018
STATUS
approved