A210999 Composite numbers that are in the gap between an odd-indexed prime and an even-indexed prime.
6, 12, 18, 24, 25, 26, 27, 28, 32, 33, 34, 35, 36, 42, 48, 49, 50, 51, 52, 60, 68, 69, 70, 74, 75, 76, 77, 78, 84, 85, 86, 87, 88, 98, 99, 100, 104, 105, 106, 110, 111, 112, 128, 129, 130, 138, 150, 158, 159, 160, 161, 162, 168, 169, 170, 171, 172
Offset: 1
Examples
Illustration of initial terms of three sequences: A210998: 4, 8, 9, 10, 14, 15, 16 A000040: 2, 3, 5, 7, 11, 13, A210999: 6, 12,
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Programs
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Mathematica
Select[Range[4, 200], Not[PrimeQ[#]] && OddQ[PrimePi[#]] &] (* Alonso del Arte, Sep 26 2012 *) Flatten[Range[First[#]+1,Last[#]-1]&/@Partition[Prime[Range[3,50]],2]] (* Harvey P. Dale, Oct 08 2012 *)