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A103001
Numbers n such that 5*10^n - 9 is prime.
2
1, 2, 4, 7, 24, 172, 173, 218, 439, 2563, 2782, 2880, 3715, 4392, 10820, 14592, 25054, 27769, 40168, 180992, 193907
OFFSET
1,2
COMMENTS
Also numbers n such that 4*10^n + 9*R_n - 8 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
a(22) > 2*10^5. - Robert Price, May 30 2015
FORMULA
a(n) = A101738(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[5*10^n - 9], Print[n]], {n, 0, 10000}]
PROG
(PARI) is(n)=ispseudoprime(5*10^n-9) \\ Charles R Greathouse IV, Jun 06 2017
CROSSREFS
Sequence in context: A099387 A359095 A036440 * A343798 A222987 A222907
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 17 2005
EXTENSIONS
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
Addition of a(17)-a(19) from Kamada data by Robert Price, Dec 10 2010
a(20)-a(21) from Robert Price, May 30 2015
STATUS
approved