A280010 Orders of consecutive clusters of non-Chen primes.

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

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