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Search: id:A108821
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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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+0
1
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| 647, 24443, 84449, 644447, 24444443, 64444444447, 2444444444443, 84444444444449, 2444444444444444444444444444443, 84444444444444444444444444444444444449
(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*4/9)*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*4/9)*10+k+1; if(isprime(y), print1(y", ")) ) ) }
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CROSSREFS
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Adjacent sequences: A108818 A108819 A108820 this_sequence A108822 A108823 A108824
Sequence in context: A067845 A057942 A046020 this_sequence A035885 A114827 A034281
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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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