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A215520 as a triangular array

1
12
123
1345
13567
14791011
14810121314
15101417181920
1512162123252627
161420272932343536
16162232354043454647
1719284045525760626364

A215520 as a square array

111111111111
22334455667
345781012141619
569101416202228
710121721273240
11131823293545
141925324052
2026344357
27354560
364662
4763
64
111111111111
22334455667
345781012141619
569101416202228
710121721273240
11131823293545
141925324052
2026344357
27354560
364662
4763
64