# weak prime

If for the given $n$th prime $p_{n}$ the inequality

 $p_{n}<{1\over 3}\sum_{i=n-1}^{n+1}p_{i}$

is true, then $p_{n}$ is said to be a weak prime. That is, the arithmetic mean of the given prime, the prime immediately below and the one immediately above, is more than the middle prime. The first few are 3, 7, 13, 19, 23, 31, 43, 47, 61, 73, 83, 89, listed in A051635 of Sloane’s OEIS.

Title weak prime WeakPrime 2013-03-22 16:36:56 2013-03-22 16:36:56 PrimeFan (13766) PrimeFan (13766) 4 PrimeFan (13766) Definition msc 11A41 BalancedPrime StrongPrime