OFFSET
1,1
COMMENTS
All primes created that way are congruent to 712 (mod 715).
Numbers in the chain may not be prime, for example 2*45757 + 3 = 91517.
The first primes congruent to 712 (mod 715) that are missed by the chain are 10007, 15727 and 18587.
On the first comment: it is easy to see that these primes are of the form 715*2^k - 3. - Bruno Berselli, May 14 2013
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..46
EXAMPLE
p = 1427, a prime, begins the sequence;
2*1427 + 3 = 2857 is prime and thus is a term.
2*2857 + 3 = 5717 is prime and thus is a term.
MAPLE
x := 1427 ; for i from 1 to 80 do if isprime(x) then printf("%d, ", x) ; end if; x := 2*x+3 ; end do: # R. J. Mathar, Aug 02 2009
MATHEMATICA
Select[NestList[2 # + 3 &, 1427, 30], PrimeQ] (* Vincenzo Librandi, May 14 2013 *)
PROG
(Magma) x:=1427; a:=[n eq 1 select x else 2*Self(n-1)+3: n in [1..100]]; [a[i]: i in [1..#a] | IsPrime(a[i])]; // Bruno Berselli, May 14 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Aug 01 2009
EXTENSIONS
Definition corrected by R. J. Mathar, Aug 01 2009
STATUS
approved