A110067 Numbers n such that 10^n + sigma(n) is prime.

1, 2, 4, 242

Offset: 1

Author

Farideh Firoozbakht, Jul 12 2005

Keywords

• more
• nonn

Comments

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

a(5) > 10^6 or it doesn't exist. - Robert Price, Mar 03 2015

Crossrefs

Cf. A110065, A110066.

Programs

Mathematica

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