Pietro Cataldi

Pietro Antonio Cataldi (1548 to 1626) was an Italian mathematician, born and buried in Bologna and a citizen of that city, who taught mathematics and astronomy and also worked on military problems. His work included the development of simple continued fractions and a method for representing them, and he was one of many mathematicians who tried to prove Euclid fifth postulate. By 1588 he had found the sixth and seventh perfect numbers, the sixth corresponding to the exponent 17 in the Mersenne formula, which overturned a long repeated belief that perfect numbers had final digits alternating between 6 and 8. His seventh, for the exponent 19, held the record for the largest known prime for almost two centuries until Euler found the eighth Mersenne prime. He wrongly claimed that further exponents also gave primes, but his text shows that he had truly established primality through the exponent 19.