OFFSET
1,1
COMMENTS
All twin primes except (3,5) have one of 3 digital root pairings: {2,4}, {5,7} or {8,1}: see A232880 for {2,4} and A232881 for {5,7}.
Twin primes of the form 9n +- 1. [Bruno Berselli, Aug 26 2014]
EXAMPLE
17 and 19 are in the sequence because they form a twin prime pair in which 17 has a digital root of 8 and 19 has one of 1. Likewise 71 and 73 form a twin prime pair where 71 has 8 for a digital root and 73 has 1.
MATHEMATICA
dRoot[n_] := 1 + Mod[n - 1, 9]; tw = Select[Prime[Range[1000]], PrimeQ[# + 2] &]; Select[Union[tw, tw + 2], MemberQ[{1, 8}, dRoot[#]] &] (* T. D. Noe, Dec 10 2013 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Gary Croft, Dec 01 2013
STATUS
approved