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A307822 The number of e-perfect numbers below 10^n. 2
0, 1, 8, 87, 871, 8690, 86940, 869417, 8694205, 86941922 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..10.

FORMULA

Lim_{n->oo} a(n)/10^n = 0.00869419399... (A318645) is the density of e-perfect numbers.

EXAMPLE

Below 10^2 there is only one e-perfect number, A054979(1) = 36, thus a(2) = 1.

MATHEMATICA

fun[p_, e_] := DivisorSum[e, p^# &]; esigma[1] = 1; esigma[n_] := Times @@ fun @@@ FactorInteger[n]; c = 0; k = 1; seq={}; Do[ While[ k < 10^n, If[ esigma[k]==2k, c++ ]; k ++]; AppendTo[seq, c], {n, 1, 5}]; seq

CROSSREFS

Cf. A051377, A054979, A318645, A307821.

Sequence in context: A225314 A200767 A222513 * A225613 A243922 A239753

Adjacent sequences:  A307819 A307820 A307821 * A307823 A307824 A307825

KEYWORD

nonn,more

AUTHOR

Amiram Eldar, Apr 30 2019

STATUS

approved

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Last modified October 18 20:20 EDT 2021. Contains 348070 sequences. (Running on oeis4.)