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A225581
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a(n) is the minimal odd prime q such that prime(n)*q + prime(n) + q is prime.
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2
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3, 5, 3, 3, 3, 5, 3, 3, 7, 5, 3, 3, 3, 5, 3, 7, 3, 11, 3, 5, 5, 5, 5, 3, 5, 11, 17, 3, 3, 5, 47, 11, 5, 5, 3, 3, 3, 5, 13, 11, 3, 3, 5, 5, 5, 11, 11, 11, 3, 3, 7, 5, 3, 5, 3, 5, 5, 3, 5, 13, 11, 7, 3, 5, 11, 5, 3, 5, 5, 3, 19, 3, 3, 5, 29, 17, 3, 23, 3, 5, 7, 5, 5, 71, 3, 5, 5, 3, 3, 47, 3, 5, 3, 11, 3, 5, 3, 3, 11, 5, 23
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OFFSET
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1,1
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LINKS
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EXAMPLE
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n = 1; p = 2; q = 3;
n = 2; p = 3; q = 5;
n = 3; p = 5; q = 3;
n = 4; p = 7; q = 3;
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MATHEMATICA
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a[n_] := Block[{q = 3, p = Prime@n}, While[! PrimeQ[p*q + p + q], q = NextPrime@q]; q]; Array[a, 101] (* Giovanni Resta, May 11 2013 *)
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PROG
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(PARI) a(n) = my(q=3, p=prime(n)); while(!isprime(p*q+p+q), q = nextprime(q+1)); q; \\ Michel Marcus, Sep 06 2021
(Python)
from sympy import isprime, nextprime, prime
def a(n):
q, p = 3, prime(n)
while not isprime(p*q + p + q): q = nextprime(q)
return q
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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