A117136 Triangle read by rows: row n always begins with 1. Later terms in row n are obtained by successively subtracting or adding the numbers n, n+1, n+2, until reaching 1 again. The rule is that you subtract if the result is positive, otherwise you add.

1, 1, 1, 2, 4, 1, 1, 3, 6, 2, 7, 1, 1, 4, 8, 3, 9, 2, 10, 1, 1, 5, 10, 4, 11, 3, 12, 2, 13, 1, 1, 6, 12, 5, 13, 4, 14, 3, 15, 2, 16, 1, 1, 7, 14, 6, 15, 5, 16, 4, 17, 3, 18, 2, 19, 1

Offset

0,4

Comments

Row n has length 2n+2.

Links

Table of n, a(n) for n=0..55.

Formula

T(n,0) = 1. For 0<k<=n+1, T(n,2k-1) = n+2-k, T(n,2k) = 2n+1+k. - Franklin T. Adams-Watters, Apr 26 2006

Example

Triangle begins:
Row 0: 1 1
Row 1: 1 2 4 1
Row 2: 1 3 6 2 7 1
Row 3: 1 4 8 3 9 2 10 1
Row 4: 1 5 10 4 11 3 12 2 13 1
...

Crossrefs

Sequence in context: A295224 A074749 A194524 * A362142 A139227 A269750

Adjacent sequences: A117133 A117134 A117135 * A117137 A117138 A117139

Keyword

nonn,tabf

Author

N. J. A. Sloane, Apr 21 2006

Status

approved