OFFSET
1,1
COMMENTS
To use Dinculescu's terminology (see links): non-ranks n such that 6n is a twin-rank.
LINKS
Jason Kimberley, Table of n, a(n) for n = 1..27455 (equivalently, a(n) < 10^6).
A. Dinculescu, On Some Infinite Series Related to the Twin Primes, The Open Mathematics Journal, 5 (2012), 8-14.
A. Dinculescu, The Twin Primes Seen from a Different Perspective, The British Journal of Mathematics & Computer Science, 3 (2013), Issue 4, 691-698.
EXAMPLE
Take n = 63; then 6n = 378 and 36n = 2268; now 379, 2267, and 2269 are prime, but 377 = 13 x 29.
MATHEMATICA
s = Select[Range@ 5184, PrimeQ[6 # - 1] && PrimeQ[6 # + 1] &]; Select[s, IntegerQ[#/6] && ! MemberQ[s, #/6] &]/6 (* Michael De Vlieger, Oct 13 2015, after N. J. A. Sloane at A002822 *)
PROG
(Magma) IsInA2822:=func<n|IsPrime(6*n-1)and IsPrime(6*n+1)>;
[n:n in[1..10^3]|not IsInA2822(n)and IsInA2822(6*n)];
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jason Kimberley, Oct 13 2015
STATUS
approved