[OS X TeX] Thu 22 June: TeX Hour: Access and a Fibonacci wedding cake: 6:30 to 7:30pm BST

[Jonathan Fine]

Thank you for this, Murray. I'd forgotten about that, even though it's
central to one of my favourite proofs (namely Peter McMullen's shelling
proof of the Dehn-Sommerville equations).

Here's what you wrote. (I'm correcting a typo and using a vert bar as it
might be more accessible than spaces).

| 1 | 1 | 1 | 1 | 1 |
| 0 | 1 | 2 | 3 | 4 |
| 0 | 0 | 1 | 3 | 6 |
| 0 | 0 | 0 | 1 | 4 |
| 0 | 0 | 0 | 0 | 1 |

Once you know the rule, it's easy to check the calculation (and hence
probably easy to state the calculation, and hence J and APL). The rule is
L-shaped, as in

| + |  . |
| + | = |

where the sum of the two | + | numbers is equal to the | = | number.

Thank you for this. It's brought back some fond memories.

Jonathan
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