From our Note: simple real function with zeros greater than one the primes
simple real function with zeros greater than one the primes: $j_1(x)=(\sin(\pi x))^2+(\sin(\pi \frac{\Gamma(x)+1}{x}))^2$. For $x>0$ the function is continuous.
$j_1$ has complex zeros for $\Re(x)>1$.
Q1 Can we remove the complex zeros while keeping the primes as zeros? Preferably we want to keep continuity.
Trying one approach. Define $f_1(x)=\sin(\pi x)$ and $f_2(x)=\sin(\pi \frac{\Gamma(x)+1}{x})$
We have $j_1(x)=f_1(x)^2+f_2(x)^2$. The complex zeros of $j_1$ which are not integers are $f_1(\rho)=\pm i \cdot f_2(\rho)$.
Assume $s$ is complex number, not an integer and $\Re(s)>1$.
Let $g(s)$ be some complex function, possibly constant.
Define $j_2(s,g(s))=g(s) f_1(s)^2 + f_2(s)^2$.
$j_2$ keeps the zeros at primes and introduces zeros
$$\sqrt{g(\rho)}=\frac{f_2(\rho)}{f_1(\rho)} \qquad (1)$$
If (1) doesn't have solution, we are done. If it has solutions for all $g$, then $\frac{f_2(\rho)}{f_1(\rho)}$ will be very close to surjective.
Another approach might be to take $F(f_1,f_2)=0$.
Observe that we allow zeros with $\Re(s) \le 1$.
Working numerically is very hard and introduces significant errors even for $s=41$.
Plot over the reals:
Here is X-Ray,$\Re(j_1(z))=0$ is plotted red and $\Im(j_1(z))=0$ is plotted blue. The intersections of the curves are zeros.
Closely related to this question.


Q1. Positive answer might not exists, but is possible to exist and it will be well defined. Negative well defined answer might exist too. I disagree that quoting paper isadvertisement, it is common practice to cite and this save space. $\endgroup$