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A056797 Numbers n such that 9*10^n+1 is prime. 7
3, 4, 5, 9, 22, 27, 36, 57, 62, 78, 201, 537, 696, 790, 905, 1038, 66886, 70500, 91836 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..19.

Makoto Kamada, Factorizations of 900...001.

Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers.

Index entries for primes involving repunits.

EXAMPLE

For n=9 we have (9*(10^9))+1 = 9000000001, which is prime.

MATHEMATICA

Do[ If[ PrimeQ[9*10^n + 1], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A056806 = 4*10^n+1 is prime.

Sequence in context: A195971 A080552 A215176 * A029727 A086186 A014463

Adjacent sequences:  A056794 A056795 A056796 * A056798 A056799 A056800

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Aug 22 2005

EXTENSIONS

a(18)-a(19) from Kamada data by Robert Price, Dec 14 2010

STATUS

approved

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Last modified December 22 14:10 EST 2014. Contains 252364 sequences.