exact-valuation reading a'(n), n=0..17: [2, 4, 3, 3, 8, 7, 7, 7, 10, 12, 11, 16, 15, 15, 15, 15, 18, 20]
'<= n' reading (= u_{n+1}),  n=0..17: [2, 4, 4, 4, 8, 8, 8, 8, 10, 12, 12, 16, 16, 16, 16, 16, 18, 20]
valuations occurring in D_1..D_6 (rows<=1500, capped view): {1: [0], 2: [0], 3: [1, 2, 3, 4, 5, 6, 7, 8], 4: [1], 5: [4, 5, 6, 7, 8, 9, 10, 11], 6: [4, 5, 6, 7, 8, 9, 10, 11]}
real 0.92
user 0.76
sys 0.01
