1,1

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

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}]

Cf. A071541.

Sequence in context: A181437 A156873 A320977 * A298764 A299562 A299459

Adjacent sequences: A071537 A071538 A071539 * A071541 A071542 A071543

nonn

Robert G. Wilson v, May 31 2002

approved