A093401 - OEIS

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A093401

Primes of the form 20*R_k + 9, where R_k is the repunit (A002275) of length k.

2

29, 229, 22229, 22222222222229

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OFFSET

1,1

COMMENTS

a(5) has 176 digits, a(6) has 416 digits. - Vincenzo Librandi, Dec 10 2010; Bruno Berselli, Jul 17 2012

LINKS

Table of n, a(n) for n=1..4.

Makoto Kamada, Prime numbers of the form 22...229.

Index entries for primes involving repunits

CROSSREFS

Cf. A002275, A056678 (corresponding k), A099410.

Sequence in context: A091631 A244767 A146421 * A228408 A042636 A372962

Adjacent sequences: A093398 A093399 A093400 * A093402 A093403 A093404

KEYWORD

nonn

AUTHOR

Rick L. Shepherd, Mar 28 2004

STATUS

approved