unary mekso operator: nth Bernoulli number B_{n} of the second kind (B_{1 }= +1/2 = >0).

Input will usually be a nonnegative integer; odd input which is greater than 1 will output 0. These numbers are very important mathematically and culturally (consider Lovelace's program). In order to transform them into Bernoulli numbers of the first kind (B_{1 }= -1/2 < 0), when the input n is a nonnegative integer, multiply by (-1)^{n} (nei'au).