A164276 The non-isolated nonprimes.

0, 1, 8, 9, 10, 14, 15, 16, 20, 21, 22, 24, 25, 26, 27, 28, 32, 33, 34, 35, 36, 38, 39, 40, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 62, 63, 64, 65, 66, 68, 69, 70, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98, 99, 100, 104, 105, 106, 110

Offset

1,3

Comments

Non-isolated nonprimes in the sense that at least one of the two adjacent integers is also a nonprime.

Links

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

Formula

A141468 \ A014574.

a(n) = n + n / log n + O(n / (log n)^2) by Brun's theorem. - Charles R Greathouse IV, Mar 15 2011

Mathematica

Select[Range[0, 100], !PrimeQ[#] && (!PrimeQ[# - 1] || !PrimeQ[# + 1]) & ] (* G. C. Greubel, Jul 07 2016 *)

Prog

(PARI) isA164276(n) = !isprime(n)&&(!isprime(n-1)||!isprime(n+1)) \\ Michael B. Porter, Feb 02 2010

Crossrefs

Cf. A014574, A141468.

Sequence in context: A067683 A338026 A359881 * A154967 A271211 A341044

Adjacent sequences: A164273 A164274 A164275 * A164277 A164278 A164279

Keyword

nonn,easy

Author

Juri-Stepan Gerasimov, Aug 11 2009

Extensions

40 added by R. J. Mathar, Aug 27 2009

Status

approved