A033559 a(n) = (q - p)/2, where p is the largest prime < n and q is the smallest prime > n.

1, 2, 1, 3, 2, 2, 2, 3, 1, 3, 2, 2, 2, 3, 1, 3, 2, 2, 2, 5, 3, 3, 3, 3, 3, 4, 1, 4, 3, 3, 3, 3, 3, 5, 2, 2, 2, 3, 1, 3, 2, 2, 2, 5, 3, 3, 3, 3, 3, 6, 3, 3, 3, 3, 3, 4, 1, 4, 3, 3, 3, 3, 3, 5, 2, 2, 2, 3, 1, 4, 3, 3, 3, 3, 3, 5, 2, 2, 2, 5, 3, 3, 3, 3, 3, 7, 4, 4, 4, 4, 4, 4, 4, 6, 2, 2, 2

Offset: 4

Author

N. J. A. Sloane

Keywords

• nonn

Links

• Jean-François Alcover, Frequency distribution up to 10^6 terms.

Programs

Mathematica

a[n_] := (NextPrime[n] - NextPrime[n, -1])/2; Table[a[n], {n, 4, 100}] (* Jean-François Alcover, Apr 16 2013 *)

Extensions

More terms from Ben Paul Thurston, Mar 30 2007