1,2

All terms are of the form k^2 or 2*k^2. There is no further term up to 16000.

Do[If[PrimeQ[10^n + DivisorSigma[1, n]], Print[n]], {n, 16000}]

Cf. A110065, A110066.

Sequence in context: A009800 A018742 A018747 this_sequence A145996 A005275 A009673

Adjacent sequences: A110064 A110065 A110066 this_sequence A110068 A110069 A110070

more,nonn

Farideh Firoozbakht (mymontain(AT)yahoo.com), Jul 12 2005