Aitken's array | Peirce triangle

1 1 2 2 3 5 5 7 10 15 15 20 27 37 52 The Bell triangle, also called Aitken's array or the Peirce triangle, is the number triangle obtained by beginning the first row with the number one, and beginning subsequent rows with last number of the previous row. Rows are filled out by adding the number in the preceding column to the number above it (OEIS A011971). The Bell numbers 1, 1, 2, 5, 15, ... (OEIS A000110) are then given as the values in the first column.

Bell number | Clark's triangle | Leibniz harmonic triangle | Losanitsch's triangle | Pascal's triangle | Seidel-Entringer-Arnold triangle

Eric Temple Bell