PARI GP is pseudoprime f(n, s)=my(t); forstep(k=n, 1, -1, t=s*t+k); t a2175=f(2175,333132); with a2175 the smallest integer s>n such that 1+2*s+3*s^2+...+n*s^{n-1} is prime OEIS A217785 Zhi Wei SUN
To be completed...