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%I #5 Dec 03 2014 20:02:09
%S 3,15,69,409,2447,16337,117959,880623,6849011,54825357,448752095,
%T 3741170439,31669329743,271560643329,2354418484607,20608371394595,
%U 181897678706317,1617351777154871
%N The number of distinct primes < 10^n which are members of twin-prime pairs.
%C Number of terms in A001097 with at most n digits.
%C The entries are odd because 5 is counted only once, although it is a member of two twin prime pairs, (3,5) and (5,7).
%C Cardinality of the set of {A001359 U A006512} with entries < 10^n. - _R. J. Mathar_, Nov 23 2009
%F a(n) = 2*A007508(n) - 1.
%e There are exactly a(2) = 15 distinct primes below 10^2 that form twin primes (p, p+2), namely,
%e 3, 5, 7, 11, 13, 17, 19, 29, 31, 41, 43, 59, 61, 71, 73 :
%e (3, 5), (5, 7), (11, 13), (17, 19), (29, 31), (41, 43), (59, 61), (71, 73).
%Y Cf. A001097, A077800, A007508.
%K nonn
%O 1,1
%A _Lekraj Beedassy_, Nov 14 2009
%E Definition rephrased by _R. J. Mathar_, Nov 23 2009
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