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A093632 Primes of the form 7*10^n + R_n, where R_n is the repunit (A002275) of length n. 1
7, 71, 71111111, 71111111111111111111111111111111111111111111111111111111 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

No further terms up to 2000 digits.  [From Harvey P. Dale, Mar 06 2012]

LINKS

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

Makoto Kamada, Prime numbers of the form 711...11.

Index entries for primes involving repunits

MATHEMATICA

Select[Table[FromDigits[PadRight[{7}, n, 1]], {n, 2000}], PrimeQ] (* Harvey P. Dale, Mar 06 2012 *)

CROSSREFS

Cf. A002275, A056719 (corresponding n).

Sequence in context: A218384 A022503 A063861 * A242827 A077332 A222833

Adjacent sequences:  A093629 A093630 A093631 * A093633 A093634 A093635

KEYWORD

nonn

AUTHOR

Rick L. Shepherd, Apr 06 2004

STATUS

approved

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Last modified August 20 14:50 EDT 2019. Contains 326152 sequences. (Running on oeis4.)