OFFSET
1,1
COMMENTS
Number of terms less than 10^k: 0, 0, 0, 1, 12, 80, 542, 3908, 29229, ... - Muniru A Asiru, Jan 29 2018
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
For the pair {1049,1051} (1049+1051)/2 = 5*210.
MAPLE
select(n->isprime(n) and isprime(n+2), [seq(210*k - 1, k=1..10^3)]); # Muniru A Asiru, Jan 29 2018
MATHEMATICA
Select[210*Range[250], And@@PrimeQ[#+{1, -1}]&]-1 (* Harvey P. Dale, Aug 25 2013 *)
PROG
(GAP) P:=Filtered([1..10^7], IsPrime);;
P1:=List(Filtered(Filtered(List([1..Length(P)-1], n -> [P[n], P[n+1]]), i -> i[2]-i[1]=2), j -> (j[1]+j[2]) mod 210 = 0), k -> k[1]); # Muniru A Asiru, Jan 29 2018
(PARI) is(n)=(n+1)%210==0 && isprime(n+2) && isprime(n) \\ Charles R Greathouse IV, Jan 29 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Mar 21 2001
EXTENSIONS
Minor edits by Ray Chandler, Apr 02 2009
STATUS
approved