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# User:William P. Orrick

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I work in mathematical physics and combinatorics. I have contributed to a number of sequences relating to (0,1) matrices, Hadamard matrices, and combinatorial designs.

Recently (as of March 2023) I have been adding sequences related to the continued fraction of *e* and to the dice problem described at A273013 and A131514.

**To-do list.** (If anyone seeing this wants to take any of these on, feel free.)

- A131514 - add cross ref. to A360098, and to A360439, A360440, if approved.
- A273013 - add cross refs. to A360439, A360440, if approved.
- A360098 - add bfile; add cross refs. to A360439, A360440, if approved.
- A168422 - formula seems to need correction: "T(n,k) = " is repeated; lower bound in summation should be
*k*, not 0; add program and bfile; add cross ref. to A360441, if approved.*(All but cross ref. to A360441 proposed for review 24 March 2023. Also an extraneous term 0 removed from sequence and some additional cross refs. added.)* - A253667 - add bfile, additional program; add cross ref. to A360441, if approved, and maybe also to A168422. Maybe also create new companion sequence whose terms are the triangle elements multiplied by
*C*(*n*,*k*). This new triangle relates more directly to A360441 and has a very nice Pascal's-triangle-like recurrence. The inverse of this new triangle, interpreted as an infinite matrix, is also interesting and could be added. The*k*= 0 column, starting with the*n*= 1 row, is -|A002119|, while the the row sums of all rows starting with*n*= 1 are 0 with all elements in columns*k*> 0 apparently positive, and possibly combinatorially meaningful. - A360439 and A360440 should cross reference each other, if both are approved. Also, bfiles should be added to both.