
EXAMPLE

The structure of this irregular triangle is shown below:
a, b, c, b;
a, b, c, b;
a, b, c, b, a, b, c, b;
a, b, c, b, a, b, c, b, a, b, c, b, a, b, c, b;
...
So, written as an irregular triangle in which the row lengths are the terms of A011782 multiplied by 4, the sequence begins:
1, 2, 4, 6;
8, 6, 12, 10;
8, 12, 18, 24, 24, 20, 30, 18;
8, 12, 18, 24, 28, 28, 46, 38, 48, 46, 68, 66, 68, 50, 72, 36;
10, 12, 18, 24, 28, 28, 46, 42, 52, 60, 80, 88,92, 90, 118, 84, 74, ...
