Problems & Puzzles: Puzzles

 Puzzle 460. Sqrt[p(x)*p(x+y)-1]= y Sebastián Martín Ruiz sent the following puzzle: Looking for solutions of this equation: Sqrt[p(x)*p(x+y)-1]= yp(x)=x-th primeSqrt=Square Root I have found three (3) solutions: x=1 y=5x=3 y=22x=10  y=186 Q. Find all solutions.

Luke Pebody wrote:

have been running the following programme in Magma:
* Set p = 2, q = 3, y = 1 and N to be the empty set.
* Start loop
* Increase y, set q = NextPrime(q)
* Set z = y*y+1
* WHILE p>2 AND z < p*q, set p = PreviousPrime(p) and q = PreviousPrime(q)
* WHILE z > p*q, set p = NextPrime(p) and q = NextPrime(q)
* If p*q = z, add the element <p,q,y> to the set N
* Print <y,N>

The latest output is
<31260000, {<2,13,5>, <5,97,22>, <29,1193,186>}

Thus there is no solution with y<31 260 000

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Enoch Haga wrote:

I have verified that the three solutions in the problem are the only
ones through n=10^7.

The question suggests that solutions may be finite. If the sequence is infinite, then each new solution I think will be found at increasingly long distances.

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