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A102996
Numbers n such that 4*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
2, 4, 26, 1271, 1412, 3328, 4676, 47051, 67664
OFFSET
1,1
COMMENTS
Also numbers n such that (43*10^n+11)/9 is prime.
a(10) > 10^5. - Robert Price, Jun 01 2015
FORMULA
a(n) = A101733(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(43*10^n + 11)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A218077 A240040 A088888 * A358563 A189896 A095182
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 17 2005
EXTENSIONS
a(8) from Erik Branger, May 01 2013, submitted by Ray Chandler, Aug 16 2013
a(9) from Robert Price, Jun 01 2015
STATUS
approved