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A068816 Primes formed by a 5 followed by 1's. 1
511111, 5111111111111, 5111111111111111, 5111111111111111111111111111111111111111111111111111111111111111111111111111111111111 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(6) has 145 digits and is too large to display here. - Vincenzo Librandi, Dec 10 2010

LINKS

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

Makoto Kamada, Prime numbers of the form 511...11.

Index entries for primes involving repunits

PROG

(PARI) for(n=1, 200, if(isprime(5*10^n+(10^(n)-1)/9)==1, print1(5*10^n+(10^(n)-1)/9, ", ")))

CROSSREFS

Cf. A002275, A056713.

Sequence in context: A249881 A205291 A205899 * A233858 A306952 A329461

Adjacent sequences:  A068813 A068814 A068815 * A068817 A068818 A068819

KEYWORD

nonn,base

AUTHOR

Amarnath Murthy, Mar 07 2002

EXTENSIONS

More terms from Benoit Cloitre, Mar 09 2002

STATUS

approved

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Last modified November 22 13:47 EST 2019. Contains 329393 sequences. (Running on oeis4.)