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

1,1

Links

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

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 *)

Prog

(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

Crossrefs

Cf. A109611.

Sequence in context: A114457 A010220 A104818 * A117540 A010221 A113172

Adjacent sequences: A280006 A280007 A280008 * A280010 A280011 A280012

Keyword

nonn

Author

Enrique Navarrete, Feb 21 2017

Status

approved