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A217131 Numbers n such that 7^n - 8 is prime. 10
2, 4, 8, 10, 50, 106, 182, 293, 964, 1108, 1654, 1756, 4601, 8870, 15100, 17446, 22742, 34570, 50150, 95276 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(21) > 10^5. - Robert Price, Jan 23 2014

LINKS

Table of n, a(n) for n=1..20.

MATHEMATICA

Select[Range[1, 5000], PrimeQ[7^#  - 8] &]

PROG

(PARI) for(n=1, 5*10^3, if(isprime(7^n-8), print1(n, ", ")))

CROSSREFS

Cf. A236371, A217131, A191469, A090669, A096305, A217130, A217132, A152213.

Sequence in context: A020950 A056386 A210108 * A116636 A256980 A014425

Adjacent sequences:  A217128 A217129 A217130 * A217132 A217133 A217134

KEYWORD

nonn

AUTHOR

Vincenzo Librandi, Oct 01 2012

EXTENSIONS

a(14)-a(20) from Robert Price, Jan 23 2014

STATUS

approved

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Last modified October 16 20:55 EDT 2019. Contains 328103 sequences. (Running on oeis4.)