OFFSET
1,2
COMMENTS
Except for the first one, all terms are multiples of 3, as can be seen from the formula a(n+1) = 3*A056956(n). - Zak Seidov, Aug 26 2012
LINKS
Jayanta Basu, Table of n, a(n) for n = 1..10000
EXAMPLE
If n = 6, then 6 + 7 = 13 and 8 + 9 = 17 are both prime.
MATHEMATICA
Select[Range[790], And @@ PrimeQ[{2*# + 1, 2*# + 5}] &] (* Jayanta Basu, Aug 11 2013 *)
Select[Range[800], AllTrue[2#+{1, 5}, PrimeQ]&] (* Harvey P. Dale, Jan 28 2023 *)
PROG
(PARI) is_A047847(n)=isprime(n*2+1)&isprime(n*2+5) \\ - M. F. Hasler, Aug 26 2012
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
EXTENSIONS
Corrected by Henry Bottomley, Jul 18 2000
STATUS
approved