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 A225581 a(n) is the minimal odd prime q such that prime(n)*q + prime(n) + q is prime. 2
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS John-Å. W. Olsen, Table of n, a(n) for n = 1..1000 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 print([a(n) for n in range(1, 102)]) # Michael S. Branicky, Sep 06 2021 CROSSREFS Cf. A000040. Sequence in context: A161670 A135514 A251754 * A275391 A092553 A112755 Adjacent sequences: A225578 A225579 A225580 * A225582 A225583 A225584 KEYWORD nonn,easy AUTHOR John-Å. W. Olsen, May 11 2013 STATUS approved

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Last modified May 24 04:41 EDT 2024. Contains 372772 sequences. (Running on oeis4.)