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A280010 Orders of consecutive clusters of non-Chen primes. 1
1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 3, 1, 1, 2, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 2, 1, 2, 1, 1, 3, 1, 2, 1, 1, 1, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

EXAMPLE

a(1)=1 since the first cluster consists of the single value p=43.

a(3)=2 since the third cluster consists of the consecutive non-Chen primes {73,79}.

MATHEMATICA

Length /@ DeleteCases[Split@ Table[Boole@ Nand[# != 1, PrimeOmega@ # <= 2] &[# + 2] &@ Prime@ n, {n, 300}], k_ /; Total@ k == 0] (* Michael De Vlieger, Feb 27 2017 *)

PROG

(PARI) do(lim)=my(v=List(), u=v, r, s); forprime(p=2, lim\2, forprime(q=2, min(lim\p, p), listput(u, p*q))); u=Set(u); r=3; forprime(p=5, lim, if(p-r==2 || setsearch(u, r+2), if(s, listput(v, s); s=0), s++); r=p); u=0; Vec(v) \\ Charles R Greathouse IV, Feb 27 2017

CROSSREFS

Cf. A102540, A280009.

Sequence in context: A043283 A127937 A250209 * A167852 A184340 A083911

Adjacent sequences:  A280007 A280008 A280009 * A280011 A280012 A280013

KEYWORD

nonn

AUTHOR

Enrique Navarrete, Feb 21 2017

STATUS

approved

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Last modified December 14 02:54 EST 2018. Contains 318087 sequences. (Running on oeis4.)