

A225581


a(n) is the minimal odd prime q such that prime(n)*q + prime(n) + q is prime.


2



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OFFSET

1,1


LINKS



EXAMPLE

n = 1; p = 2; q = 3;
n = 2; p = 3; q = 5;
n = 3; p = 5; q = 3;
n = 4; p = 7; q = 3;


MATHEMATICA

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 *)


PROG

(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


CROSSREFS



KEYWORD

nonn,easy


AUTHOR



STATUS

approved



