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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 (list; graph; refs; listen; history; text; internal format)
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: A248235 A327345 A049050 * 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

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Last modified April 14 00:07 EDT 2021. Contains 342941 sequences. (Running on oeis4.)