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A128027
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Numbers n such that (11^n - 3^n)/8 is prime.
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20
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3, 5, 19, 31, 367, 389, 431, 2179, 10667, 13103, 90397
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| All terms are primes.
No other terms <100,000.
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MATHEMATICA
| k=8; Select[ Prime[ Range[1, 200] ], PrimeQ[ ((k+3)^# - 3^#)/k ]& ]
Do[If[PrimeQ[(11^n - 3^n)/8], Print[n]], {n, 10^4}] (* Ryan Propper (rpropper(AT)stanford.edu), Mar 17 2007 *)
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CROSSREFS
| Cf. A028491 = numbers n such that (3^n - 1)/2 is prime. Cf. A057468 = numbers n such that 3^n - 2^n is prime. Cf. A059801 = numbers n such that 4^n - 3^n is prime. Cf. A121877 = numbers n such that (5^n - 3^n)/2 is a prime. Cf. A128024, A128025, A128026, A128028, A128029, A128030, A128031, A128032.
Sequence in context: A088785 A068990 A062594 * A128066 A148523 A148524
Adjacent sequences: A128024 A128025 A128026 * A128028 A128029 A128030
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KEYWORD
| hard,more,nonn
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AUTHOR
| Alexander Adamchuk (alex(AT)kolmogorov.com), Feb 11 2007
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EXTENSIONS
| a(8) from Ryan Propper (rpropper(AT)stanford.edu), Mar 17 2007
a(9) from Farideh Firoozbakht (mymontain(AT)yahoo.com), Apr 04 2007
a(10)=13103, a(11)=90397 from Robert Price (pamandbobprice(AT)yahoo.com), Apr 24 2011
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