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Ordered Matrices Of Prescribed Row And Column Sum, Janine Janoski

All Theses

Let M(n,s) be the number of nxn matrices with binary entries, row and column sum s, and whose rows are in lexicographical order. Let S(n) be the number of nxn matrices with entries from {0,1,2}, symmetric, with trace 0, and row sum 2. (The sequence S(n) appears as A002137 in N.J.A. Sloane's Online Encyclopedia of Integer Sequences.)
We give two proofs to show that M(n,2)=S(n). First, we show they satisfy the same recurrence. Second, we give an explicit bijection between the two sets. We also show that the bijection maintains the cycle structure of our matrices.
Let M_s(n,2) be the …