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

1,2

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

Links

Table of n, a(n) for n=1..12.

Mathematica

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

Crossrefs

Cf. A072394, A178321.

Sequence in context: A327345 A049050 A344020 * A165161 A098858 A213995

Adjacent sequences: A178319 A178320 A178321 * A178323 A178324 A178325

Keyword

more,nonn

Author

Farideh Firoozbakht, May 26 2010

Extensions

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

Status

approved