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

Author

Eric Angelini, Mar 11 2009

Keywords

• base
• nonn

Comments

The triangular numbers fitting exactly in a "triangulars-digits triangle" are given by A158030. Terms computed by Jean-Marc Falcoz.

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]