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A117136
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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.
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2
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| Row n has length 2n+2.
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FORMULA
| T(n,0) = 1. For 0<k<=n+1, T(n,2k-1) = n+2-k, T(n,2k) = 2n+1+k. - Frank Adams-Watters (FrankTAW(AT)Netscape.net), Apr 26 2006
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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
...
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CROSSREFS
| Sequence in context: A158570 A074749 A194524 * A139227 A065626 A201758
Adjacent sequences: A117133 A117134 A117135 * A117137 A117138 A117139
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KEYWORD
| nonn,tabf
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Apr 21 2006
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