Brown is fascinated by numbers and how they can be magical and mystical. The Lost Symbol literally revolves around the number 33 as it is used in Masonic rites and rituals. The very title contains 13 letters. Inferno has seven letters. The publication date is 5/14/13. The numbers placed one after another 51413 are an inversion of the decimal value of the number PI (3.1413), used to determine the circumference and area of circles.
In The DaVinci Code and The Lost Symbol, Brown referred to Magic Squares and the Fibonacci sequence. On his revised website for the novel, under SECRETS, you can type in “PYTHAGORAS” as a key to open a door that is a concealed video. A similar result can be achieved by typing in TETRACTYS (an anagram of TARTY SECT). He also refers to the Biblical book of Job 38:11. (“And said, Hitherto shalt thou come, but no further: and here shall thy proud waves be stayed?”).
There is likely to be much more to come centered around Fibonacci and Pythagoras or the Pythagoreans. This latter group receives special attention in a work that Brown has used in the past, Manly P. Hall’s 1928 Secret Teaching of All Ages.