A260409 - OEIS

%I #14 Aug 16 2015 15:14:14

%S 8,16,18,27,45,50,54,60,64,84,99,132,147,153,162,207,220,225,228,240,

%T 242,243,245,255,256,264,280,297,315,325,336,338,343,348,364,369,375,

%U 423,425,435,440,455,460,468,475,477,486,487,507,539,552

%N Bisection of A260310.

%C Greater (member) of the n-th pair in A260310.

%C a(n) ~ 11.0*n.

%C It appears that most of the terms are composite (97.25% out of the first 10000 terms), but there are some primes: 487, 983, 1093, 1231, 1277, 2143, 2207, 2749, ..., .

%C a(n) < a(n+1) for all n > 0 is false, a(3276) = a(3277)= 35407 with A260409(3276) equal to 29820 & A260409(3276) equal to 34350 and a(4228) = a(4229) = 45841 with A260409(4228) equal to 40260 & A260409(4229) equal to 41496.

%C Least term a(n) such that a(n+1) is k away: 3276, 21, 2, 18, 6, 5, 7, 44, 1, 3, ..., . (A260410).

%C Conjecture: when a(n) is composite, A260408(n) is prime and vice versa. No contradictions in the first 10000 terms.

%H Robert G. Wilson v, <a href="/A260409/b260409.txt">Table of n, a(n) for n = 1..9906</a>

%F a(n) = A260310(2n).

%e see A260310.

%t (* first run the Mmca in A260310 and then *) Take[ Transpose[ lst][[2]], 60]

%Y Cf. A260310, A260408, A260410.

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Jul 24 2015