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A178322
Numbers n such that 156/101*(10^(4n)-1)-1 is prime.
2
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
MATHEMATICA
Select[Range[700], PrimeQ[156/101*(10^(4 #) - 1) - 1] &]
CROSSREFS
Sequence in context: A327345 A049050 A344020 * A165161 A098858 A213995
KEYWORD
more,nonn
AUTHOR
Farideh Firoozbakht, May 26 2010
EXTENSIONS
a(8)-a(12) from Robert Price, May 23 2014
STATUS
approved