A167705 Composite numbers having four composite nearest neighbors.

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

Harvey P. Dale, Table of n, a(n) for n = 1..10000

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

Cf. A002808, A079364.

Sequence in context: A349733 A100393 A133635 * A061673 A072571 A307033

Adjacent sequences: A167702 A167703 A167704 * A167706 A167707 A167708

Keyword

nonn,easy

Author

Juri-Stepan Gerasimov, Nov 10 2009

Extensions

Comment and program from Charles R Greathouse IV, Nov 12 2009

Corrected terms, Clark Kimberling and Joerg Arndt, Jun 24 2011.

Status

approved