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A071541 Number of k's less than or equal to 10^n such that there are middle divisors of k (A071090). 1
6, 43, 336, 2932, 26870, 252756, 2409731 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..7.

MATHEMATICA

f[n_] := Plus @@ Select[ Divisors[n], Sqrt[n/2] <= # < Sqrt[n*2] &]; s = 0; k = 0; Do[ While[k < 10^n, k++; If[ f[k] != 0, s++ ]]; Print[s], {n, 1, 7}]

CROSSREFS

Cf. A071540.

Sequence in context: A098665 A153397 A005786 * A146966 A240653 A220097

Adjacent sequences:  A071538 A071539 A071540 * A071542 A071543 A071544

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, May 31 2002

STATUS

approved

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Last modified April 8 20:49 EDT 2020. Contains 333325 sequences. (Running on oeis4.)