A071540 - OEIS

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A071540

Number of k's less than or equal to 10^n such that there are no middle divisors of k (A071090).

4, 57, 664, 7068, 73130, 747244, 7590269 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,1`
	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. A071541.` `Sequence in context: A193745 A181437 A156873 * A103907 A108148 A099348` `Adjacent sequences: A071537 A071538 A071539 * A071541 A071542 A071543`
	KEYWORD	`nonn`
	AUTHOR	`Robert G. Wilson v (rgwv(AT)rgwv.com), May 31 2002`

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Last modified February 17 19:13 EST 2012. Contains 206085 sequences.