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A172409 Numbers n such that neither n-2 nor n-3 is prime. 0
0, 1, 2, 3, 11, 12, 17, 18, 23, 24, 27, 28, 29, 30, 35, 36, 37, 38, 41, 42, 47, 48, 51, 52, 53, 54, 57, 58, 59, 60, 65, 66, 67, 68, 71, 72, 77, 78, 79, 80, 83, 84, 87, 88, 89, 90, 93, 94, 95, 96, 97, 98, 101, 102, 107, 108, 113, 114, 117, 118, 119, 120, 121, 122, 123, 124 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..66.

FORMULA

a(n) ~ n. - Charles R Greathouse IV, Jun 13 2017

EXAMPLE

a(1)=0 because 0-2=-2 and 0-3=-1 are nonprime.

MATHEMATICA

Join[{0, 1}, Select[Range[150], !PrimeQ[#-2]&&!PrimeQ[#-3]&]] (* 0 and 1 are in the sequence because primes are usually defined to include only positive integers, but because Mathematica treats many negative numbers, including -2 and -3, as primes, it is necessary to include 0 and 1 via "Join". *) (* Harvey P. Dale, Aug 06 2012 *)

PROG

(PARI) is(n)=!isprime(n-2) && !isprime(n-3) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Sequence in context: A116029 A060812 A212129 * A062936 A136972 A227764

Adjacent sequences:  A172406 A172407 A172408 * A172410 A172411 A172412

KEYWORD

nonn,easy,less

AUTHOR

Juri-Stepan Gerasimov, Feb 06 2010

EXTENSIONS

Corrected by Charles R Greathouse IV, Mar 25 2010

STATUS

approved

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Last modified June 20 05:01 EDT 2019. Contains 324229 sequences. (Running on oeis4.)