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A102995
Numbers n such that 4*10^n + 7*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
1, 22, 925, 2340, 15955, 16098, 55512, 82752
OFFSET
1,2
COMMENTS
Also numbers n such that (43*10^n-61)/9 is prime.
a(9) > 10^5. - Robert Price, Jun 01 2015
FORMULA
a(n) = A101732(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(43*10^n - 61)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A345456 A322930 A200575 * A211887 A041927 A041924
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 17 2005
EXTENSIONS
Two more PRP terms from Serge Batalov, Feb 15 2009
a(7)-a(8) from Robert Price, Jun 01 2015
STATUS
approved