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A261459
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Numbers k such that the concatenation of k 1's, the digits of k^2 + k + 1, and k 1's is prime.
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0
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1, 3, 4, 5, 6, 10, 254, 410, 751, 1101, 2488, 3476, 14124, 20060
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OFFSET
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1,2
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COMMENTS
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Numbers k that generate the terms in A263299.
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LINKS
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PROG
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(Python)
from gmpy2 import is_prime
A261459_list = [k for k in range(10**3) if is_prime(int('1'*k+str(k*(k+1)+1)+'1'*k))]
(PARI) for(n=1, 1e3, if(isprime(eval(Str((10^n - 1)/9, n^2 + n + 1, (10^n - 1)/9))), print1(n", "))); \\ Altug Alkan, Oct 20 2015
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CROSSREFS
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KEYWORD
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nonn,base,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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