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A289357
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Least number k such that n^2 + n - k is prime.
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1
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0, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 5, 1, 11, 1, 1, 13, 5, 1, 1, 1, 3, 5, 1, 3, 1, 5, 1, 7, 1, 1, 5, 5, 3, 1, 5, 7, 1, 1, 3, 1, 5, 3, 1, 1, 1, 5, 1, 3, 1, 5, 3, 1, 1, 1, 1, 5, 9, 1, 1, 3, 17, 5, 1, 1, 1, 7, 1, 13, 1, 5, 19, 3, 19, 7, 1, 19, 11, 3, 7, 5, 3, 1, 11, 1
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OFFSET
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1,7
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COMMENTS
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LINKS
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FORMULA
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MAPLE
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0, seq(n^2 + n - prevprime(n^2+n), n=2..100); # Robert Israel, Jul 03 2017
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MATHEMATICA
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Table[k = 0; While[! PrimeQ[n^2 + n - k], k++]; k, {n, 85}] (* Michael De Vlieger, Jul 04 2017 *)
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PROG
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(PARI) for(n=1, 85, k={my(k=0); while(!isprime(n^2+n-k), k++); k; }; print1(k", "))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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