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A093675 Primes of the form 7*10^n + 3*R_n, where R_n is the repunit (A002275) of length n. 2
7, 73, 733, 7333, 733333, 733333333333333333333333333333333333333333333333333333, 733333333333333333333333333333333333333333333333333333333 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The next term (a(8)) has 344 digits. - Harvey P. Dale, Nov 11 2014

LINKS

Table of n, a(n) for n=1..7.

Makoto Kamada, Prime numbers of the form 733...33.

Index entries for primes involving repunits

MATHEMATICA

Select[Table[FromDigits[PadRight[{7}, n, 3]], {n, 500}], PrimeQ] (* Harvey P. Dale, Nov 11 2014 *)

PROG

(MAGMA) [a: n in [0..200] | IsPrime(a) where a is (22*10^n-1) div 3 ]; // Vincenzo Librandi, May 08 2019

CROSSREFS

Cf. A002275, A056720 (corresponding n).

Sequence in context: A009142 A155614 A113033 * A121127 A071060 A092444

Adjacent sequences:  A093672 A093673 A093674 * A093676 A093677 A093678

KEYWORD

nonn

AUTHOR

Rick L. Shepherd, Apr 08 2004

STATUS

approved

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Last modified December 9 19:51 EST 2019. Contains 329879 sequences. (Running on oeis4.)