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A178322
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Numbers n such that 156/101*(10^(4n)-1)-1 is prime.
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2
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1, 2, 5, 29, 30, 108, 679, 4478, 8736, 17000, 22427, 22731
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OFFSET
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1,2
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COMMENTS
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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
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LINKS
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Table of n, a(n) for n=1..12.
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MATHEMATICA
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Select[Range[700], PrimeQ[156/101*(10^(4 #) - 1) - 1] &]
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CROSSREFS
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Cf. A072394, A178321.
Sequence in context: A248235 A327345 A049050 * A165161 A098858 A213995
Adjacent sequences: A178319 A178320 A178321 * A178323 A178324 A178325
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KEYWORD
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more,nonn
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AUTHOR
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Farideh Firoozbakht, May 26 2010
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EXTENSIONS
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a(8)-a(12) from Robert Price, May 23 2014
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STATUS
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approved
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