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A273010 Numbers n such that (9^n - 7^n)/2 is prime. 0
3, 5, 7, 4703, 30113 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms are prime.

The corresponding primes: 193, 21121, 1979713, ...

LINKS

Table of n, a(n) for n=1..5.

MATHEMATICA

Select[Range[1, 10000], PrimeQ[(9^# - 7^#)/2] &]

PROG

(PARI) for(n=1, 10000, if(isprime((9^n - 7^n)/2), print1(n, ", ")))

CROSSREFS

Cf. A081202, A173718, A128346, A059803.

Sequence in context: A191546 A069463 A288212 * A073691 A110336 A073695

Adjacent sequences:  A273007 A273008 A273009 * A273011 A273012 A273013

KEYWORD

nonn,more,hard

AUTHOR

Tim Johannes Ohrtmann, May 13 2016

STATUS

approved

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Last modified May 23 20:23 EDT 2019. Contains 323528 sequences. (Running on oeis4.)