A178322 Numbers n such that 156/101*(10^(4n)-1)-1 is prime.

1, 2, 5, 29, 30, 108, 679, 4478, 8736, 17000, 22427, 22731

Offset: 1

Author

Farideh Firoozbakht, May 26 2010

Keywords

• more
• nonn

Comments

If n is in the sequence then m=91*(156/101*(10^(4n)-1)-1) is a term of A072394. Namely if n is a term of this sequence then for m=1/101*(14196*10^(4n)-23387), we have sigma(m)=reversal(m)-m (see comment lines of A072394).

Numbers corresponding to the larger terms are probable primes.

Next term exceeds 3500. - Robert G. Wilson v, Aug 08 2011.

a(13) > 40000. - Robert Price, May 23 2014

Crossrefs

Cf. A072394, A178321.

Programs

Mathematica

Select[Range[700], PrimeQ[156/101*(10^(4 #) - 1) - 1] &]

Extensions

a(8)-a(12) from Robert Price, May 23 2014