Prime Numbers theory

Consider triples (p,q,r) of prime numbers p, q and r such that (p+1)(q+1)=(r+1). here are some exmaples : (2,3,11), (3,7,31). how to prove these triples are infinitely?! I define two integer numbers n and m or (n,m) to be Isomorph iff F(n)=F(m). F(n) is sum of divisor of n. for example (6,11) , (10,17) , (14, 23), (21, 31).If for prime numbers p,q,r have :(p+1)(q+1)=(r+1) so (pq,r) are isomorph and so it maybe a conjecture: there are infinitely pairs of isomorph numbers!

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