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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 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.)