Pure NW-SE chain:

The "one cxtn SE" graphic starts the chain in the NW
Then up to three "cxtn NW&SE" graphics
Then "one cxtn NW" graphic to end
If there's more, repeat the pattern

If there are 5n+1 mountains in the chain, the last one (most SE)
is a standalone mountain.

However, it's not entirely clear where in each NW-Se row the 
"beginning of length 5 chain" can begin.



Pure NE-SW chain

We take a look at the chain going SW from (0, 0).
The patterns of its lengths is:
?1, 1, 5 (ending 94, 6), 5 (ending 89, 11), 2, 3 (ending 84, 13), 4 (ending 80, 20), 1, 1, 4 (ending 74, 26), 1, 4, 2, 1 (ending 66, 34), 2, 
5, 3 (ending 56, 44), 2, 2, 3 (ending 49, 51)4, 1, 5 (ending 39, 61), 1, 4, 3 (ending 31, 69), 2, 5, 1 (ending 23, 77), 4, 2, 3 (ending 14, 86)
, 2, 2, 1 (ending 9, 91), 5, 1, 2? (final, 1,99)

Discounting the first and last we have

1, 5, 5, 2, 3, 4, 1, 1, 4, 1, 4, 2, 1, 2, 5, 3, 2, 2, 3, 4, 1, 5, 1, 4, 3, 2, 5, 1, 4, 2, 3, 2, 2, 1, 5, 1 -> should total 97
check to (80, 20), check to (56, 44), check to (39, 61), check to (23, 77), check to 91 == 97 check

Looking at the one starting at (72, 0) we have
5 (for sure), 2, 3, 4, 1, 1, 4, 1 (ending (52, 20))
oh! this does correspond with the 5,2,3,4,1,1,4,1 pattern in the one starting at (0, 0)
Now the question is how do we get 5,2,3,4,1,1,4,1!?!?!?!?
Copying again and making sure it extends further

5 (for sure), 2, 3, 4, 1, 1, 4, 1 (ending (52, 20)), 4, 2, 1 (ending (45, 27), 2, 5, 3 (ending (35, 37)
5 (for sure), 2, 3, 4, 1, 1, 4, 1, 4, 2, 1, 2, 5, 3 
Yes, this is definitely a pattern that's repeated

Now let's look at the (96, 0) chain

1?, 3, 2, 5 (ending (86, 10)), 5, 2, 3, 1 (ending (75, 21)), 3, 1, 5, 1, 1 (ending 64, 32)3, 3, 2 (ending (56, 40)), 3, 2, 5, 2 (end 44, 52),
   2, 1, 4, 1 (end 36, 60), 5, 1, 4 (end 26, 70), 3, 2, 1, 4 (end 16, 80), 5, 2, 3, 4, 1 (end 1, 95), 4?
==
1?, 3, 2, 5, 5, 2, 3, 1, 3, 1, 5, 1, 1, 3, 3, 2, 3, 2, 5, 2, 2, 1, 4, 1, 5, 1, 4, 3, 2, 1, 4, 5, 2, 3, 4, 1, 4?

Hmm.. no immediately obvious overlap.  But surely there is a pattern.

(72, 0) started at exactly 2 mountains farther into the chain than (0, 0) did.

I wonder about (36, 0)...

Chain starting at (36, 0)

1?, 5, 1, 1, 3, 4, 1 (ending 21, 15)
No overlap except possibly with the very end of the chain starting at (0, 0)

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Checking a large map, we unfortunately have some bad news.
The chain at (0, 0) doesn't follow the same pattern as on a Standard map.
It does a 2?, 1, 2, 2, 5, 2, 5

The chain at (100, 0) does:
1?, 1, 5, 5, 2, 3 (ending 84, 16)

Whew!  So it appears that the pattern does hold, just that (0, 0) isn't the base for it.
Mayhaps (0, maxY) is the base for a pattern?

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Mountain Patterns 4 and 5 demonstrate that a chain going NE from (0, 98) is the same on both a Standard and Large map.

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Back to Mountain Patterns 3.  (52, 0) has starts with 5, just like (72, 0) [(92, 0), annoyingly, does not]

It goes:
5, 1, 4, 1, 2 (end 40, 12), 2, 5, 2, 3, 2 (end 26, 26), 3, 3, 1, 1 (end 18, 34), 5, 1, 3, 1 (end 8, 44),
3, 2, 4, 3 (end 95, 57), 2, 5, 2, 2, 1 (end 83, 69), 4, 1, 5, 1, 4 (end 68, 84), 3, 2, 1, 4, 5 (end)
Thus far that doesn't appear to match a pattern - (later) oh but that's wrong!  It matches with (2, 0)!

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Now let's see if this makes any sense.  Purely NW-SE ranges are difficult to find.  But let's look at the Icelandic (26,8) to (27, 9) chain on
Paasky's WWII.  Those mountains infuriated me by not connecting.  But by extending the range starting at (18, 0) on Mountain Patterns 2.biq,
we can see that indeed, by the NW-SE chain rules, they do not connect!  They are simply following those rules.

If we can determine the overarching NE-SW rules as well, we should be able to figure out the total pattern.  Unfortunately it looks like we'll
need a lot of data to figure that one out.

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98:
2?, 2, 2, 3 (ending 90, 8), 5, 2, 1 (end 82, 16), 2, 4, 1, 4, 1, 1 (end 69, 29), 4, 3, 2, 5 (end 55, 43), 5, 1, 1, 3 (end 45, 53),
4, 1, 2, 3, 1, 4 (end 30, 68), 3, 2, 5, 4, 1 (end 15, 83), 2, 3, 4, 1, 5, 1?

Pattern!  In 100, we have 41141421.  We have 12414114 in 98!  We have a reverse element in here

Maybe we can generalize this somehow...

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94:

3?, 2, 1, 2, 5 (end 82, 12), 3, 2, 2, 3, 4, 1 (end 67, 27), 5, 1, 4, 3 (end 54, 40), 2, 5, 1, 4, 2 (end 40, 54), 3, 2, 2, 1, 5, 1 (end 26, 68)
2, 2, 3, 2, 4, 1 (end 12, 82), 5, 2, 3 (end 2, 92), 3, 2, 1?

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2:
4?, 2, 3, 2, 3 (end 88, 14), 3, 1, 1, 5, 1, 3, 1 (end 73, 29), 3, 2, 5, 5 (end 58, 44), 2, 3, 1, 3, 1, 5, 1 (end 42, 60), 1, 3, 3, 2,
3, 2 (end 28, 74), 5, 2, 2, 1, 4, 1 (end 13, 89), 5, 1, 4?

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99, 1 -> (-23, +29) = 66, 30.  Which is in (96, 0).  Unfortunately the pattern doesn't repeat there

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(6, 0) start - but work back from (7, 99) this time - _reverse_
1?, 3, 4, 1, 5 (end 20, 86), 1, 4, 3, 2, 2 (end 32, 74), 3, 5, 2, 1, 2 (end 45, 61), 4, 1, 4, 1, 1, 4 (end 60, 46), 3, 2, 5, 5 (end 76, 31), 1, 1, 3,
4, 1, 2, 3 (end 90, 16), 1, 4, 3 (end 98, 8), 2, 1, 2, 1, 1?
