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A103096
Numbers n such that 9*10^n + 3*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
1
0, 1, 2, 3, 4, 15, 27, 71, 86, 105, 242, 250, 448, 539, 784, 814, 1025, 1172, 1353, 3009, 3175, 3682, 6993, 7612, 7780, 9633, 27109, 27735, 28767, 61574
OFFSET
1,3
COMMENTS
Also numbers n such that (28*10^n+11)/3 is prime.
a(31) > 10^5. - Robert Price, Nov 07 2015
FORMULA
a(n) = A101005(n-1) + 1, for n>1.
EXAMPLE
For n=0, (28*10^n+11)/3 = 13, which is prime.
MATHEMATICA
Do[ If[ PrimeQ[(28*10^n + 11)/3], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A135633 A269725 A270929 * A295757 A005645 A362639
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
a(26)-a(28) from Kamada data by Robert Price, Dec 14 2010
Inserted a(1)=0 and added a(30) by Robert Price, Nov 07 2015
STATUS
approved