A302992 Number of abundant numbers < 10^n.

0, 21, 245, 2487, 24794, 247544, 2476736, 24760667, 247610954, 2476238920, 24761949212, 247617948446, 2476198914588, 24762008009145, 247619645317536, 2476194603970937, 24761962442728106

Offset

1,2

Links

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

Formula

Limit_{n->oo} a(n)/10^n = 0.2476... is the density of abundant numbers (A302991).

Mathematica

abQ[n_]:=DivisorSigma[1, n]>2n; c = 0; k = 1;  seq={}; Do[ While[ k < 10^n, If[ abQ[k], c++ ]; k ++]; AppendTo[seq, c], {n, 1, 5}]; seq

Prog

(PARI) a(n) = sum(k=1, 10^n-1, sigma(k) > 2*k); \\ Michel Marcus, Apr 17 2018

Crossrefs

Cf. A000203, A005101, A302991.

Sequence in context: A271792 A177730 A199300 * A344919 A165095 A165099

Adjacent sequences: A302989 A302990 A302991 * A302993 A302994 A302995

Keyword

nonn,more

Author

Amiram Eldar, Apr 17 2018

Extensions

a(10) from Daniel Suteu, Apr 22 2018

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

Status

approved