A158031 Sides of equilateral triangles which are filled exactly (no holes, no overlaps) by the digits used to write a subsequence of consecutive triangular numbers, starting with 0.
1, 2, 3, 4, 8, 9, 11, 12, 14, 17, 22, 25, 30, 33, 36, 38, 41, 43, 46, 48, 51, 53, 56, 58, 61, 63, 65, 66, 69, 74, 77, 78, 81, 86, 89, 90, 93, 98, 101, 102, 105, 110, 113, 114, 117, 122, 125, 126, 132, 133, 139, 140, 146, 147, 153, 154, 160, 161, 167, 168, 174, 175, 181
Offset: 1
Examples
...0....0....0.....0 ........13...13....13 .............610...610 ...................1521 The above "equilateral" triangles, filled exactly by a subsequence of consecutive triangular numbers starting with 0 have sides 1, 2, 3, 4. The next properly filled triangle will have side 8.
Links
- Eric Angelini, Digit Spiral
- E. Angelini, Digit Spiral [Cached copy, with permission]
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