A098014 A098013/2.

2, 2, 2, 3, 3, 2, 2, 3, 3, 3, 2, 3, 2, 3, 2, 2, 2, 7, 2, 3, 5, 3, 3, 2, 3, 3, 5, 2, 2, 2, 3, 5, 3, 3, 3, 3, 2, 5, 7, 2, 2, 7, 3, 5, 2, 3, 3, 3, 2, 3, 2, 5, 5, 3, 2, 3, 2, 2, 2, 2, 3, 3, 5, 3, 3, 3, 5, 3, 3, 3, 3, 2, 5, 2, 3, 3, 2, 3, 5, 5, 3, 3, 2, 3, 2, 2, 7, 5, 5, 2, 5, 7, 2, 2, 7, 2, 2, 2, 5, 2, 3, 3, 7, 2, 3

Offset

1,1

Comments

Half the difference between consecutive primes is prime.

(1/2)(29 - 23) = 3, the 4th entry in the table.

Links

Table of n, a(n) for n=1..105.

Mathematica

Select[Differences[Prime[Range[250]]]/2, PrimeQ] (* Harvey P. Dale, Dec 20 2012 *)

Prog

(PARI) f(n) = for(x=1, n, y=prime(x+1)-prime(x); if(isprime(y\2), print1(y\2", ")))
(Magma) [ a: n in [1..2500] | IsPrime(a) where a is ((NthPrime(n+1)-NthPrime(n)) div 2 )]; // Vincenzo Librandi, Apr 19 2011

Crossrefs

Sequence in context: A348470 A317369 A096916 * A059957 A361088 A165924

Adjacent sequences: A098011 A098012 A098013 * A098015 A098016 A098017

Keyword

easy,nonn

Author

Cino Hilliard, Sep 09 2004

Status

approved