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A108828
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Primes such that the outer 2 digits are n and n+1 and all inner digits are 9, where 0 < n < 9.
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0
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293, 6997, 8999, 69997, 299993, 6999997, 89999999, 29999999993, 69999999997, 89999999999999999999, 699999999999999999997, 299999999999999999999999999993, 899999999999999999999999999999
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OFFSET
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1,1
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LINKS
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FORMULA
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a(x) = 10^(x+1)*n+(10^x-1)*10+n+1. Output if a(x) is prime.
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PROG
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(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", ")) ) ) }
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CROSSREFS
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KEYWORD
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easy,nonn,base
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AUTHOR
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STATUS
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approved
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