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A108821
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Primes such that the outer 2 digits are n and n+1 and all inner digits are 4, where 0 < n < 9.
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1
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OFFSET
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1,1
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LINKS
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Harvey P. Dale, Table of n, a(n) for n = 1..27
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FORMULA
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a(x) = 10^(x+1)*n+floor(10^x*4/9)*10+n+1. Output if a(x) is prime.
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MATHEMATICA
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Select[Sort[Flatten[Table[FromDigits[Join[{n}, PadRight[{}, m, 4], {n+1}]], {n, 8}, {m, 40}]]], PrimeQ] (* Harvey P. Dale, Mar 17 2019 *)
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PROG
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(PARI) n10np1(n) = { local(x, y, k); for(x=1, n, for(k=1, 8, y=10^(x+1)*k+floor(10^x*4/9)*10+k+1; if(isprime(y), print1(y", ")) ) ) }
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CROSSREFS
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Sequence in context: A250989 A187434 A046020 * A345702 A035885 A114827
Adjacent sequences: A108818 A108819 A108820 * A108822 A108823 A108824
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KEYWORD
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easy,nonn,base
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AUTHOR
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Cino Hilliard, Jul 11 2005
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STATUS
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approved
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