1,1

E.g. a(2) = 3*3 = 9: divisors of 9 are 1, 3, 9, all of which are lucky numbers.

Cf. A057600, A000959.

Sequence in context: A109285 A091760 A144525 this_sequence A046239 A093351 A018543

Adjacent sequences: A087670 A087671 A087672 this_sequence A087674 A087675 A087676

nonn

Vit Planocka (planocka(AT)mistral.cz), Sep 26 2003