Legendres conjecture

 What is legrande's conjecture?

def isprime(num):

    for i in range(2,num+1):

        if num%i:

            return True

        return False

i=int(input("Enter A number "))

l=list(range(i*i,(i+1)*(i+1)))

t=filter(isprime,l)

print("prime numbers in the range ",i*i,"",(i+1)*(i+1),"are ")

for c in t:

    print(c)