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A145851 Primes of the form k followed by k 9's. 2
19, 49999, 599999, 1799999999999999999, 2099999999999999999999, 289999999999999999999999999999 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Corresponding k, which cannot be multiples of 3, are in A174352. The next term has 176 digits, too large to include here. - Rick L. Shepherd, Mar 22 2010

LINKS

Table of n, a(n) for n=1..6.

PROG

(PARI) lista(nn) = for(k=1, nn, if(ispseudoprime(q=k*10^(k-1)-1), print1(q, ", "))); \\ Jinyuan Wang, Mar 24 2020

CROSSREFS

Cf. A141311, A145852.

Cf. A174352. - Rick L. Shepherd, Mar 22 2010

Sequence in context: A203703 A068734 A216529 * A182374 A034207 A098970

Adjacent sequences:  A145848 A145849 A145850 * A145852 A145853 A145854

KEYWORD

nonn,base

AUTHOR

Lekraj Beedassy, Oct 21 2008

EXTENSIONS

a(2) was 4999; corrected by Rick L. Shepherd, Mar 22 2010

STATUS

approved

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Last modified May 17 06:30 EDT 2021. Contains 343965 sequences. (Running on oeis4.)