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A303736 Number of deficient numbers < 10^n. 1
8, 76, 751, 7508, 75201, 752451, 7523259, 75239327, 752389040, 7523761073, 75238050781, 752382051546, 7523801085404, 75237991990847, 752380354682456, 7523805396029055, 75238037557271886 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Lim_{n->oo} a(n)/10^n = 0.752... is the density of deficient numbers (A005100).

LINKS

Table of n, a(n) for n=1..17.

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

Cf. A005100, A302992.

Sequence in context: A096293 A239549 A247828 * A083234 A247744 A144851

Adjacent sequences:  A303733 A303734 A303735 * A303737 A303738 A303739

KEYWORD

nonn,more

AUTHOR

Muniru A Asiru, May 19 2018

EXTENSIONS

a(11)-a(17) from Hiroaki Yamanouchi, Aug 03 2018

STATUS

approved

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Last modified November 22 06:15 EST 2019. Contains 329389 sequences. (Running on oeis4.)