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A097684
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Numbers n such that (10^n-1)/9 + 6 is prime.
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3
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1, 2, 4, 5, 8, 23, 29, 40, 131, 136, 215, 611, 767, 2153, 2576
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Values indicate primes of the form "(n-1) ones followed by a seven". Related to the base 10 repunit primes.
Some of the larger entries may only correspond to probable primes.
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LINKS
| Index entries for primes involving repunits
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FORMULA
| a(n) = A056655(n) + 1 for all n >= 0.
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MATHEMATICA
| Do[ If[ PrimeQ[(10^n - 1)/9 + 6], Print[n]], {n, 0, 5000}] (from Robert G. Wilson v Oct 14 2004)
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PROG
| (PARI) for (i=1, 1000, if(isprime((10^i-1)/9 + 6), print1(i, ", "), print1("."))) (Bouayoun)
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CROSSREFS
| Cf. A004023, A056655, A097683, A097685.
Sequence in context: A045591 A045581 A092061 * A171411 A092752 A152603
Adjacent sequences: A097681 A097682 A097683 * A097685 A097686 A097687
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KEYWORD
| nonn
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AUTHOR
| Carl R. White (cyrek(AT)cyreksoft.yorks.com), Aug 19 2004
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EXTENSIONS
| a(12) and a(13) from Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), Aug 23 2004.
a(12)-a(15) from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Aug 23 2004
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