1,2

usigma[x]=288, invusigma[288]={138, 154, 165, 168, 213, 235, 248, 253}, so a(288)=8, the number of all terms in the inverse set and all similar numbers are larger:{288, 648, 672, 900}.

Cf. A051444, A054973, A057637, A034444, A034448.

Sequence in context: A097704 A098585 A087105 this_sequence A001335 A145899 A001041

Adjacent sequences: A063972 A063973 A063974 this_sequence A063976 A063977 A063978

nonn

Labos E. (labos(AT)ana.sote.hu), Sep 05 2001