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
Programs
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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 -
PARI
a(n) = sum(k=1, 10^n-1, sigma(k) > 2*k); \\ Michel Marcus, Apr 17 2018
Formula
Limit_{n->oo} a(n)/10^n = 0.2476... is the density of abundant numbers (A302991).
Extensions
a(10) from Daniel Suteu, Apr 22 2018
a(11)-a(17) from Hiroaki Yamanouchi, Aug 03 2018