%N Mean gap between successive primes up to n-th prime is an integer.
%H C. K. Caldwell, <a href="http://primes.utm.edu/glossary/page.php?sort=PrimeGaps">Prime Gaps</a>
%F n such that (n - 1) divides (prime(n) - n - 1), or equivalently,
%F n such that (n - 1) divides (prime(n) - 2).
%e a(2)=10 since 9 (number of gaps) divides 18 (number of composites less than 29, the 10th prime). Therefore the "average" gap less than 29 is exactly 2.
%Y Cf. A049038, A049066, A228543.
%A _G. L. Honaker, Jr._
%E More terms from Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), May 25 2000
%E Three more terms from _Phil Carmody_, Jul 23 2003