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A102946
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Numbers n such that 2*10^n-7 is prime.
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2
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1, 2, 3, 4, 6, 16, 21, 28, 48, 82, 122, 130, 282, 304, 4602, 12984, 13614, 42762, 90597
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Also numbers n such that 10^n + 9*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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LINKS
| Makoto Kamada, Factorizations of 199...993.
Index entries for primes involving repunits.
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MATHEMATICA
| Do[ If[ PrimeQ[2*10^n - 7], Print[n]], {n, 0, 10000}]
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CROSSREFS
| Sequence in context: A204540 A002087 A049288 * A026094 A069860 A084391
Adjacent sequences: A102943 A102944 A102945 * A102947 A102948 A102949
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KEYWORD
| more,nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 16 2004
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EXTENSIONS
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
Addition of a(18)-a(19) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 10 2010
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