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A277124
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Numbers k such that (k+1)*prime(k) + k is a prime.
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1
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1, 2, 3, 5, 6, 8, 9, 11, 13, 14, 20, 21, 26, 29, 30, 33, 35, 36, 39, 41, 43, 49, 54, 55, 62, 68, 69, 75, 76, 79, 81, 89, 90, 105, 110, 113, 117, 119, 126, 134, 141, 146, 154, 162, 174, 176, 178, 179, 186, 191, 195, 207, 209, 215, 216, 222, 225, 227, 230, 231, 234, 237
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OFFSET
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1,2
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LINKS
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MAPLE
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p:= 1: count:= 0: Res:= NULL:
for n from 1 while count < 100 do
p:= nextprime(p);
if isprime(n*p+n+p) then
count:= count+1; Res:= Res, n
fi
od:
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MATHEMATICA
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npQ[n_]:=Module[{p=Prime[n]}, PrimeQ[n*p+n+p]]; Select[Range[250], npQ] (* Harvey P. Dale, Mar 27 2022 *)
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PROG
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(PARI) is(n) = isprime((n + 1) * (prime(n) + 1) - 1); \\ Altug Alkan, Oct 01 2016
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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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