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A167705
Composite numbers having four composite nearest neighbors.
2
26, 34, 50, 56, 64, 76, 86, 92, 93, 94, 116, 117, 118, 119, 120, 121, 122, 123, 124, 134, 142, 143, 144, 145, 146, 154, 160, 170, 176, 184, 185, 186, 187, 188, 202, 203, 204, 205, 206, 207, 208, 214, 215, 216, 217, 218, 219, 220, 236, 244, 245, 246, 247, 248, 254, 260, 266, 274, 286, 287, 288, 289, 290, 296, 297, 298, 299, 300
OFFSET
1,1
COMMENTS
Almost all natural numbers are members of this sequence.
LINKS
EXAMPLE
a(1)=26 (24,25,27,28 are composite nearest neighbors), a(2)=34 (32,33,35,36 are composite nearest neighbors).
MATHEMATICA
Select[Range[6!], !PrimeQ[#]&&!PrimeQ[#-1]&&!PrimeQ[#+1]&&!PrimeQ[#-2]&&!PrimeQ[#+2]&] (* Vladimir Joseph Stephan Orlovsky, Dec 26 2010 *)
Flatten[Position[Partition[PrimeQ[Range[310]], 5, 1], _?(Union[#]=={False}&), {1}, Heads->False]]+2 (* Harvey P. Dale, Nov 01 2013 *)
PROG
(PARI) for(n=4, 1e4, if(n-precprime(n)>2&&nextprime(n)-n>2, print1(n", ")))
CROSSREFS
Sequence in context: A349733 A100393 A133635 * A061673 A072571 A307033
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Comment and program from Charles R Greathouse IV, Nov 12 2009
Corrected terms, Clark Kimberling and Joerg Arndt, Jun 24 2011.
STATUS
approved