Start with a(0) = a(1) = 1. If a(n) = n is the rightmost term defined so far, let a(m) = m := n + a(n-1). If the terms between a(n) and a(m) are undefined, let a(n+1) = a(n) + a(m) and if m > n+1, a(m-1) = a(n+1) + a(m).

A333375

Start with a(0) = a(1) = 1. If a(n) = n is the rightmost term defined so far, let a(m) = m := n + a(n-1). If the terms between a(n) and a(m) are undefined, let a(n+1) = a(n) + a(m) and if m > n+1, a(m-1) = a(n+1) + a(m).