Erdős Problem #423

`IsConsecutiveBlockSum a k m` means that \(m\) equals the sum of at least two consecutive terms of the sequence \(a\), using indices from \(\{1, \ldots, k - 1\}\). That is, there exist \(i, j\) with \(1 \le i\), \(i + 1 \le j\), \(j \le k - 1\) such that \(m = a(i) + a(i+1) + \cdots + a(j)\).

The Hofstadter sequence (OEIS A005243): \(a(1) = 1\), \(a(2) = 2\), and for \(k \ge 3\), \(a(k)\) is the least integer \(> a(k-1)\) that equals the sum of at least two consecutive terms from \(\{a(1), \ldots, a(k-1)\}\). The sequence begins \(1, 2, 3, 5, 6, 8, 10, 11, \ldots\).