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A173772 as a simple table

na(n)
17
247
3447
44447
544447
6444447
74444447
844444447
9444444447
104444444447
1144444444447
12444444444447
134444444444447
1444444444444447
15444444444444447
164444444444444447
1744444444444444447
18444444444444444447
194444444444444444447
2044444444444444444447
21444444444444444444447

[7,47,447,4447,44447,444447,4444447,44444447,
 444444447,4444444447,44444444447,444444444447,
 4444444444447,44444444444447,444444444444447,
 4444444444444447,44444444444444447,
 444444444444444447,4444444444444444447,
 44444444444444444447,444444444444444444447]