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A026820 as a triangular array

1
12
123
1345
13567
14791011
14811131415
15101518202122
1512182326282930
161423303538404142
16162737444952545556
1719344758

A026820 as a square array

111111111111
22334455667
345781012141619
569111518232734
710131823303747
11142026354458
1521283849
22294052
304154
4255
56

A026820 as an upper right triangle

111111111111
22334455667
345781012141619
569111518232734
710131823303747
11142026354458
1521283849
22294052
304154
4255
56

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Last modified November 26 21:55 EST 2014. Contains 250123 sequences.