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A079364 Composite numbers having two composite neighbors. 6
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

In other words, composite numbers that are not nearest-neighbors of primes. - Omar E. Pol, Jan 02 2009

Complement of A210940. - Omar E. Pol, Apr 18 2012

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

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 *)

PROG

(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

CROSSREFS

Cf. A000040, A002808, A014574, A045718.

Cf. A010051, A221309 (subsequence).

Sequence in context: A038599 A321342 A255763 * A160666 A039769 A270574

Adjacent sequences:  A079361 A079362 A079363 * A079365 A079366 A079367

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Feb 15 2003

STATUS

approved

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Last modified December 11 23:44 EST 2019. Contains 329945 sequences. (Running on oeis4.)