A039644 Number of steps to fixed point of "k -> k/2 or (k+1)/2 until result is prime", starting with prime(n)-1.

1, 1, 2, 2, 2, 3, 4, 3, 2, 3, 5, 4, 4, 3, 2, 3, 2, 6, 3, 5, 5, 5, 2, 4, 6, 4, 4, 2, 5, 5, 7, 4, 4, 6, 3, 4, 6, 3, 2, 3, 2, 4, 7, 7, 5, 5, 3, 6, 2, 4, 4, 8, 8, 8, 8, 2, 3, 5, 7, 7, 3, 3, 7, 7, 7, 3, 3, 6, 2, 6, 6, 2, 5, 4, 8, 2, 3, 6, 6, 6, 4, 4, 7, 7, 7, 7, 7, 5, 5, 5, 2, 2, 4, 5, 9, 2, 3, 6, 3, 6, 3, 3