login
A103049
Numbers n such that 7*10^n-3 is prime.
1
1, 3, 4, 6, 10, 20, 51, 138, 190, 360, 378, 393, 1384, 1594, 2759, 2868, 5395, 7494, 10491, 11199, 12190, 33594, 38256, 89169, 165916
OFFSET
1,2
COMMENTS
Also numbers n such that 6*10^n + 9*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
a(26) > 2*10^5. - Robert Price, Aug 17 2015
FORMULA
a(n) = A101542(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[7*10^n - 3], Print[n]], {n, 0, 10000}]
PROG
(PARI) is(n)=ispseudoprime(7*10^n-3) \\ Charles R Greathouse IV, Jun 12 2017
CROSSREFS
Sequence in context: A353138 A052548 A232268 * A103016 A061032 A091424
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 18 2005
EXTENSIONS
a(19)-a(24) from Kamada data by Robert Price, Dec 14 2010
a(25) from Robert Price, Aug 17 2015
STATUS
approved