A079364 Composite numbers having two composite neighbors.
9, 15, 21, 25, 26, 27, 33, 34, 35, 39, 45, 49, 50, 51, 55, 56, 57, 63, 64, 65, 69, 75, 76, 77, 81, 85, 86, 87, 91, 92, 93, 94, 95, 99, 105, 111, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 129, 133, 134, 135, 141, 142, 143, 144, 145, 146, 147, 153, 154, 155
Offset: 1
Keywords
Links
- Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
Programs
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Haskell
a079364 n = a079364_list !! (n-1) a079364_list = filter (\x -> a010051' (x - 1) == 0 && a010051' (x + 1) == 0) a002808_list -- Reinhard Zumkeller, Jan 10 2013
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Mathematica
Select[Range[6! ],!PrimeQ[ # ]&&!PrimeQ[ #-1]&&!PrimeQ[ #+1]&] (* Vladimir Joseph Stephan Orlovsky, Apr 26 2010 *) With[{r=Complement[Range[160],Prime[Range[PrimePi[160]]]]}, Transpose[ Select[ Partition[r,3,1], Differences[#]=={1,1}&]][[2]]] (* Harvey P. Dale, Feb 05 2012 *) Mean/@SequencePosition[Table[If[CompositeQ[n],1,0],{n,200}],{1,1,1}] (* Harvey P. Dale, May 10 2025 *)
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