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A101395
Numbers n such that 4*10^n+7 is prime.
1
0, 1, 3, 9, 39, 2323
OFFSET
1,3
COMMENTS
No further terms < 50000.
a(7) > 2*10^5. - Robert Price May 16 2015
FORMULA
a(n) = A101714(n-1) + 1.
EXAMPLE
n = 1, 3, 9 are members since 47, 4007 and 4000000007 are primes.
MATHEMATICA
Do[ If[ PrimeQ[4*10^n + 7], Print[n]], {n, 0, 10000}]
PROG
(PARI) is(n)=ispseudoprime(4*10^n+7) \\ Charles R Greathouse IV, Jun 12 2017
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005
STATUS
approved