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A108828 Primes such that the outer 2 digits are n and n+1 and all inner digits are 9, where 0 < n < 9. 0
293, 6997, 8999, 69997, 299993, 6999997, 89999999, 29999999993, 69999999997, 89999999999999999999, 699999999999999999997, 299999999999999999999999999993, 899999999999999999999999999999 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..13.

FORMULA

a(x) = 10^(x+1)*n+(10^x-1)*10+n+1. Output if a(x) is prime.

PROG

(PARI) n10np9(n, d) = { local(x, y, k); for(x=1, n, for(k=1, 8, y=10^(x+1)*k+(10^x-1)*10+k+1; if(isprime(y), print1(y", ")) ) ) }

CROSSREFS

Sequence in context: A109182 A241047 A085502 * A239825 A145206 A153579

Adjacent sequences:  A108825 A108826 A108827 * A108829 A108830 A108831

KEYWORD

easy,nonn,base

AUTHOR

Cino Hilliard, Jul 11 2005

STATUS

approved

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Last modified October 17 11:47 EDT 2019. Contains 328108 sequences. (Running on oeis4.)