

A164276


The nonisolated nonprimes.


13



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
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OFFSET

1,3


COMMENTS

Nonisolated 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(n1)!isprime(n+1)) \\ Michael B. Porter, Feb 02 2010


CROSSREFS

Cf. A014574, A141468.
Sequence in context: A114842 A169928 A067683 * A154967 A271211 A072381
Adjacent sequences: A164273 A164274 A164275 * A164277 A164278 A164279


KEYWORD

nonn,easy


AUTHOR

JuriStepan Gerasimov, Aug 11 2009


EXTENSIONS

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


STATUS

approved



