Let {b(m)} be Recamán's sequence A005132, with the additional term b(-1):=0. Define a(n) to be the first index m where b(m-1)-m = -n, or -1 if b(m-1)-m never equals -n.

A375118

Let {b(m)} be Recamán's sequence A005132, with the additional term b(-1):=0. Define a(n) to be the first index m where b(m-1)-m = -n, or -1 if b(m-1)-m never equals -n.