A280009 Orders of consecutive clusters of Chen primes.

13, 3, 2, 2, 1, 8, 1, 1, 3, 3, 1, 2, 4, 1, 3, 1, 2, 2, 1, 1, 3, 1, 2, 1, 8, 1, 6, 1, 1, 2, 3, 2, 1, 1, 2, 2, 5, 3, 1, 3, 1, 2, 4, 4, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 3, 1, 1, 2, 5, 1, 3, 3, 1, 1

Offset: 1

Author

Enrique Navarrete, Feb 21 2017

Keywords

• nonn

Links

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

Crossrefs

Cf. A109611.

Programs

Mathematica

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

PARI

do(lim)=my(v=List(),u=v,r,s=1); 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), s++, if(s, listput(v, s); s=0)); r=p); u=0; Vec(v) \\ Charles R Greathouse IV, Feb 27 2017