If a+1,a+2 and a+4 are prime numbers, then the number of possible solutions for a is:
The given primes are a+1,a+2 and a+4. Now (a+2)−(a+1)=1 and (a+4)−(a+2)=2. The only set of primes which are separated by 1 and 2 are 2,3,5. ∴a+1=2⇒a=1