A167692 The even nonisolated nonprimes.

0, 8, 10, 14, 16, 20, 22, 24, 26, 28, 32, 34, 36, 38, 40, 44, 46, 48, 50, 52, 54, 56, 58, 62, 64, 66, 68, 70, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 104, 106, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 136, 140, 142, 144, 146, 148

Offset: 1

Author

Juri-Stepan Gerasimov, Nov 09 2009

Keywords

• nonn
• easy
• less

Comments

Zero together with A100319, the even numbers n such that at least one of n-1 and n+1 is composite.

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A100319, A164276.

Programs

Mathematica

Select[Range[0, 100], Mod[#, 2] == 0 && !PrimeQ[#] && (! PrimeQ[# - 1] || !PrimeQ[# + 1]) &] (* G. C. Greubel, Jul 07 2016 *)
Join[{0},Select[Range[2,150,2],AnyTrue[#+{1,-1},CompositeQ]&]] (* Harvey P. Dale, Nov 10 2024 *)

PARI

isA167692(n) = (n%2==0)&&!isprime(n)&&(!isprime(n-1)||!isprime(n+1)) \\ Michael B. Porter, Feb 02 2010

Extensions

Edited by Charles R Greathouse IV, Mar 22 2010