Analysis reveals unique solutions to nested recurrence relations in integers, indicating deep combinatorial connections.
A family of nested recurrence relations a(n+1) = n - a⁽ᵐ⁾(n) + a⁽ᵐ⁺¹⁾(n), parameterized by an integer m ≥ 1 with initial condition $a(1)=1$, is studied. We prove that $a(n)=n-h(n)$ is the unique solution satisfying this condition, where $h(n)$ is an arithmetical sequence in which each non-negative integer k appears $mk+1$ times, with $h(n)$ 1-indexed such that $h(1)=0$. An explicit floor formula for $h(n)$ (and thus for $a(n)$) is derived. The proof of the main theorem involves establishing a key identity for $h(n)$ that arises from the recurrence; this identity is then proved using arithmetical properties of $h(n)$ and the iterated function a⁽ᵐ⁾(n) at critical boundary points. Combinatorial interpretations for $a(n)$ and its partial sums (for $m=2$), and connections to The On-Line Encyclopedia of Integer Sequences (OEIS), including generalizations of Connell's sequence, are also discussed.
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Benoit Cloitre (2025) studied this question.
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