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A102956
Numbers n such that 2*10^n + 5*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
1, 82, 322, 733, 2431, 8386, 15886, 19912
OFFSET
1,2
COMMENTS
Also numbers n such that (23*10^n+31)/9 is prime.
a(9) > 10^5. - Robert Price, Feb 06 2015
FORMULA
a(n) = A101963(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(23*10^n + 31)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A227704 A248405 A116341 * A031696 A005972 A082972
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Dec 17 2004
EXTENSIONS
Addition of a(7)-a(8) from Kamada data by Robert Price, Dec 13 2010
STATUS
approved