Mathematics is a language of science. Math begins with simple proofs. Within any numeration system rational number n is multiplied by rational number m obtaining rational number mn. Proof is obtained by a division method that inverts m to 1/m to prove that mn times 1/m must return n.
Modular arithmetic rules were used by Mayans. Mayans used its rational number system within black and red numbers reporting a seasonal almanac in the Dresden Codex (pages 61-69).
A 405-moon lunar calendar is included A 1988 paper written by the Brickers. The Brickers decoded pages 65-68 of the Dresden Code as an eclipse, solstice and equinox almanac valid for nearly 1,000 years (per 15 reference dates mentioned on pages 61-64).
Bruce Friedman in 2012 reports shorter seasonal 1898, 1898, 1924 and 1911 day cycles on pages 65-68.
A new first line (summed to 1898) needs to be decoded to fully read this data.
Friedman argues for a four line matrix of raw data across pages 65-68, with the last three lines possibly reporting:
a series that is under review by adding in the first line of four lines.
Note that the symmetry is not perfect because 178 "appears" where 177 is "expected", without 148 being mentioned. Line two that referred to an anomaly (namely line 2 on p.65 where 13,11 appears to break a consistent pattern of 10 day mod 13 additions to alternate entries in all of lines one and two. 13,10 is "expected" b the pattern and would have made the 178 "appears" as 177.
The Bricker's corrected this anomaly as a scribal error, a conclusion that has not been refuted.
The matrix almanac numbers were processed from the first two lines only but yield 163 (twice) and 167 (once at middle).
163 and 167 are obscure but may be an anchor (of some kind) to the third line where the same values "appear" as a delta from the first and last entries on line 3 p.65 (167 as the delta between 9,9 and 1,2) and the first and last entries of line 3 p.67 (163 as the delta between 11,5 and 3,2). Shelving analysis of these two quantities [163 and 167]
in favor of the more peculiar four-time appearance of 432 seems important. To date 4 x 432 is 1728 and trivially is
1000 + (2 x 364).
However: Line three's 13 quantities total 1911 which is 21 x 91 and if 1728 id deducted 183 as a result. Also look at
432 less one cycle of 260 and find result 172. 172+183 is 355. 355 "appears" above (as I believe it was intended) to be the 177+178 spacing of lunar eclipses. The 432 day number appears four times in a manner that needs to be precisely understood.
The other matrix numbers are associated with well-known lunar eclipse cycles.
Mayans added red and black numbers as other keys, possibly in the Canary Island acano manner, another issue that calls out to be studied.
Mayan astronomers worked from the mid-year season, outwards, denoted by feet icons going forward and back, and year bearers as the Brickers' 2011 book. The matrix data double checked and proved almanac data by several techniques, the details of which are under investigation.