A071541 Number of k's less than or equal to 10^n such that there are middle divisors of k (A071090).

6, 43, 336, 2932, 26870, 252756, 2409731

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