A159800 Triangle read by rows in which row n contains a finite triangle as shown below.

1, 1, 2, 2, 2, 3, 2, 1, 2, 2, 1, 1, 2, 2, 3, 3, 3, 3, 4, 4, 3, 3, 4, 5, 4, 3, 2, 3, 4, 4, 3, 2, 1, 2, 3, 3, 3, 2, 1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 4, 4, 5, 6, 6, 5, 4, 4, 5, 6, 7, 6, 5, 4, 3, 4, 5, 6, 6, 5, 4, 3, 2, 3, 4, 5, 5, 5, 4, 3, 2, 1, 2, 3, 4, 4, 4, 4, 3, 2, 1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5

Offset

1,3

Links

Table of n, a(n) for n=1..105.

Example

The main triangle begins:
1,
1,2,2,2,3,2,1,2,2,1,
1,2,2,3,3,3,3,4,4,3,3,4,5,4,3,2,3,4,4,3,2,1,2,3,3,3,2,1,
1,2,2,3,3,3,4,4,4,4,4,5,5,5,4,4,5,6,6,5,4,4,5,6,7,6,5,4,3,4,5,6,6,5,4,3,...
In which row 1 contains a vertex, only:
1
Row 2 contains the triangle:
1
2,2
2,3,2
1,2,2,1
Row 3 contains the triangle:
1
2,2
3,3,3
3,4,4,3
3,4,5,4,3
2,3,4,4,3,2
1,2,3,3,3,2,1
Row 4 contains the triangle:
1
2,2
3,3,3
4,4,4,4
4,5,5,5,4
4,5,6,6,5,4
4,5,6,7,6,5,4
3,4,5,6,6,5,4,3
2,3,4,5,5,5,4,3,2
1,2,3,4,4,4,4,3,2,1
Row 5 contains the triangle:
1
2,2
3,3,3
4,4,4,4
5,5,5,5,5
5,6,6,6,6,5
5,6,7,7,7,6,5
5,6,7,8,8,7,6,5
5,6,7,8,9,8,7,6,5
4,5,6,7,8,8,7,6,5,4
3,4,5,6,7,7,7,6,5,4,3
2,3,4,5,6,6,6,6,5,4,3,2
1,2,3,4,5,5,5,5,5,4,3,2,1
And so on...

Crossrefs

Sequence in context: A014843 A116987 A219838 * A273021 A365722 A071137

Adjacent sequences: A159797 A159798 A159799 * A159801 A159802 A159803

Keyword

easy,nonn,tabf

Author

Omar E. Pol, Nov 09 2009

Status

approved