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%I #13 Oct 08 2012 21:36:55
%S 6,12,18,24,25,26,27,28,32,33,34,35,36,42,48,49,50,51,52,60,68,69,70,
%T 74,75,76,77,78,84,85,86,87,88,98,99,100,104,105,106,110,111,112,128,
%U 129,130,138,150,158,159,160,161,162,168,169,170,171,172
%N Composite numbers that are in the gap between an odd-indexed prime and an even-indexed prime.
%H Harvey P. Dale, <a href="/A210999/b210999.txt">Table of n, a(n) for n = 1..1000</a>
%e Illustration of initial terms of three sequences:
%e A210998: 4, 8, 9, 10, 14, 15, 16
%e A000040: 2, 3, 5, 7, 11, 13,
%e A210999: 6, 12,
%t Select[Range[4, 200], Not[PrimeQ[#]] && OddQ[PrimePi[#]] &] (* _Alonso del Arte_, Sep 26 2012 *)
%t Flatten[Range[First[#]+1,Last[#]-1]&/@Partition[Prime[Range[3,50]],2]] (* _Harvey P. Dale_, Oct 08 2012 *)
%Y Cf. A002808, A014689, A031215, A031368, A073170, A210998.
%K nonn,easy
%O 1,1
%A _Omar E. Pol_, Sep 26 2012