This is easy to do with [PARI/GP](https://pari.math.u-bordeaux.fr/). Here is my code ``` p(n) = binomial(n+2,2); Y(k,b) = sumnum(l=0, (2*l+3)/(p(k)+p(l))^b); Z(a,b) = sumnum(k=0, (2*k+3)/p(k)^a*Y(k,b)); default(realprecision,57); print(2*Z(2,2)+4*Z(1,3)) /* 16.0000000000000000000000000000000000000000000000000000000 */ ``` It takes four seconds for 57 decimal places. The [documentation](https://pari.math.u-bordeaux.fr/doc.html) has some information about the methods being used and there are several summation functions other than `sumnum`. For example, I originally used `sumpos` but `sumnum` is better.