%I #14 Aug 16 2015 15:14:03
%S 3,7,11,7,17,29,41,53,31,71,29,107,61,41,131,53,157,113,179,239,131,
%T 79,73,127,127,229,223,113,199,73,317,181,43,269,241,89,193,101,89,
%U 211,331,167,313,409,97,113,401,480,193,109,457,241,431
%N Bisection of A260310.
%C Lesser (member) of the n-th pair in A260310.
%C Most of the terms are prime, 97.25%, but there are composites, 2.75%: 480, 960, 990, 1200, 1170, 1950, 1890, 2610, ..., . They seem to all be congruent 0 (mod 6).
%C Conjecture: when a(n) is prime, A260409(n) is composite and vice versa. No contradictions in the first 10000 terms.
%C A260408 sorted without repeats: 3, 7, 11, 17, 29, 31, 41, 43, 53, 61, 71, 73, 79, 89, 97, 101, ..., .
%C Primes that have not appeared yet (10000 terms examined): 2, 5, 13, 19, 23, 37, 47, 59, 67, 83, 103, 139, 151, 163, 191, 197, ..., .
%H Robert G. Wilson v, <a href="/A260408/b260408.txt">Table of n, a(n) for n = 1..9906</a>
%F a(n) = A260310(2n-1).
%e See A260310.
%t (* first run the Mmca in A260310 and then *) Take[ Transpose[ lst][[1]], 75]
%Y Cf. A260310, A260409, A260410.
%K nonn
%O 1,1
%A _Robert G. Wilson v_, Jul 24 2015
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