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Results tagged with co.combinatorics
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user 153549
Enumerative combinatorics, graph theory, order theory, posets, matroids, designs and other discrete structures. It also includes algebraic, analytic and probabilistic combinatorics.
6
votes
1
answer
278
views
Another generalization of parity of Catalan numbers
Recently, a question by T. Amdeberhan gathered up many enjoyable proofs that a Catalan number $C_n$ is odd if and only if $n=2^r-1$.
Noam D. Elkies' answer considered $F=\sum_{n=0}^\infty C_n x^{n+1}$ …
- 524
6
votes
Accepted
Congruences for power-sum of divisors
I wrote an answer in the comment section, so I'll rewrite it here.
The claim of
$$F_1(q)-F_3(q)\equiv F_1(q^p) \pmod p$$
is equivalent to the following two cases
$$p\nmid n: \sum_{d|n} d-nd^3 \equiv …
- 524