OFFSET
1,1
COMMENTS
a(11) > 8695354111. - Donovan Johnson, Sep 27 2008
LINKS
D. H. Lehmer, On certain chains of primes, Proc. London Math. Soc. (3) 14a 1965 183-186.
EXAMPLE
a(3) = 5 because 5 is the beginning of 3 primes in succession: 5, 3*5 + 2 = 17 is prime and 3*17 + 2 = 53 is prime.
MATHEMATICA
c[p_] := Block[{k=1, q = 3 p + 2}, While[PrimeQ[q], q = 3 q + 2; k++]; k]; a[n_] := Block[{p=2}, While[c[p] < n, p = NextPrime[p]]; p]; Array[a, 7] (* Giovanni Resta, Mar 21 2017 *)
PROG
(PARI) mx=1; forprime(p=1, 198000, x=p; m=0; while(isprime(x=3*x+2), m=m+1; if(m>mx, print(p, " ", m, " ", x); mx=m, ))) \\ Donald S. McDonald, Jun 11 2003
CROSSREFS
KEYWORD
nonn
AUTHOR
W. Edwin Clark, Jun 09 2003
EXTENSIONS
a(8)-a(10) from Donovan Johnson, Sep 27 2008
a(11)-a(12) from John Cerkan, Jan 09 2017
a(13)-a(14) from Giovanni Resta, Mar 21 2017
STATUS
approved