A216075 Numbers n such that 2*prime(n) - prime(n+1) is prime.

3, 4, 9, 15, 16, 21, 37, 40, 47, 51, 55, 56, 71, 74, 103, 108, 111, 114, 118, 119, 130, 161, 165, 180, 184, 185, 188, 195, 200, 208, 219, 227, 231, 232, 238, 239, 240, 255, 267, 272, 273, 274, 278, 290, 292, 317, 326, 340, 354, 359, 381, 388, 392, 396, 416

Offset: 1

Author

Zak Seidov, Sep 06 2012

Keywords

• nonn

Comments

Corresponding values of 2*prime(n) - prime(n+1) are in A215808.

Links

• Zak Seidov, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A215808.

Programs

Mathematica

f[n_]:=(2Prime[n]-Prime[n+1]); Select[Range[1000],PrimeQ[f[#]]&]
Position[Partition[Prime[Range[500]],2,1],?(PrimeQ[2#[[1]]-#[[2]]]&), 1,Heads->False]//Flatten (* _Harvey P. Dale, Apr 06 2018 *)

PARI

list(lim)=my(v=List(),n,p=2); forprime(q=3,, if(n++>lim, return(Vec(v))); if(isprime(2*p-q), listput(v,n)); p=q) \\ Charles R Greathouse IV, May 22 2017