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Search: id:A108824
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| A108824 |
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Primes such that the outer 2 digits are n and n+1 and all inner digits are 7, where 0 < n < 9. |
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+0
1
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| 677, 8779, 27773, 67777, 8777779, 27777777773, 67777777777, 67777777777777, 67777777777777777777777777, 87777777777777777777777777777779, 8777777777777777777777777777777777779
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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a(x) = 10^(x+1)*n+floor(10^x*7/9)*10+n+1. Output if a(x) is prime.
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PROGRAM
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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*7/9)*10+k+1; if(isprime(y), print1(y", ")) ) ) }
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CROSSREFS
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Sequence in context: A142755 A031614 A031730 this_sequence A097773 A031524 A097771
Adjacent sequences: A108821 A108822 A108823 this_sequence A108825 A108826 A108827
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KEYWORD
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easy,nonn,base
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Jul 11 2005
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