OFFSET
1,1
COMMENTS
a(4)..a(7) are the first set of 4 prime-indexed primes in arithmetic progression: a(4) = 353 = prime(prime(20)); a(5) = 431 = prime(prime(23)); a(6) = 509 = prime(prime(25)); a(7) = 587 = prime(prime(28)). Then we can see that 431-353 = 509-431 = 587-509 = 78. - Bobby Jacobs, Nov 30 2016
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
FORMULA
a(n) ~ 24n log n. - Charles R Greathouse IV, Jul 03 2016
MATHEMATICA
Select[Prime[Range[3000]], MemberQ[{2}, Mod[#, 39]]&] (* Vincenzo Librandi, Aug 19 2012 *)
Select[Range[2, 9000, 39], PrimeQ] (* Harvey P. Dale, Oct 21 2014 *)
PROG
(Magma)[p: p in PrimesUpTo(9000) | p mod 39 eq 2 ]; // Vincenzo Librandi, Aug 19 2012
(PARI) is(n)=isprime(n) && n%39==2 \\ Charles R Greathouse IV, Jul 03 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jul 11 2008
STATUS
approved