A302993 - OEIS

A302993

Number of unitary abundant numbers < 10^n.

0, 5, 64, 691, 7011, 70030, 699597, 7005450, 70048740, 700321813, 7003128054, 70034216605, 700350142296, 7003426996800, 70033987968599, 700341098675985, 7003416399263312

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OFFSET

1,2

LINKS

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

FORMULA

Conjecture: Lim_{n->oo} a(n)/10^n = 0.07... is the density of unitary abundant numbers.

MATHEMATICA

usigma[n_] := If[n == 1, 1, Times @@ (1 + Power @@@ FactorInteger[n])]; uabQ[n_] := usigma[n] > 2 n; c = 0; k = 1; seq={}; Do[While[k < 10^n, If[uabQ[k], c++]; k++]; AppendTo[seq, c], {n, 1, 5}]; seq

CROSSREFS

Cf. A034448, A034683, A302992.

Sequence in context: A351855 A178295 A054937 * A266095 A255523 A193222

Adjacent sequences: A302990 A302991 A302992 * A302994 A302995 A302996

KEYWORD

nonn,more

AUTHOR

Amiram Eldar, Apr 17 2018

EXTENSIONS

a(10)-a(17) from Hiroaki Yamanouchi, Aug 03 2018

STATUS

approved