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Search: id:A161009
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| A161009 |
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Tribonacci left-bounded rhombic triangle. |
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+0
1
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| 1, 1, 1, 3, 2, 1, 7, 7, 3, 1, 18, 20, 12, 4, 1, 48, 59, 40, 18, 5, 1, 132, 174, 132, 68, 25, 6, 1, 372, 517, 426, 247, 105, 33, 7, 1, 1069, 1548, 1362, 864, 415, 152, 42, 8, 1, 3121, 4670, 4332, 2956, 1561, 648, 210, 52, 9, 1, 9232, 14188, 13746, 9960, 5685, 2604, 959, 280
(list; table; graph; listen)
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OFFSET
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0,4
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FORMULA
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Riordan array ((1/(1-x-x^2-x^2))*c((x/(1-x-x^2-x^3))^2),(x/(1-x-x^2-x^2))*c((x/(1-x-x^2-x^3))^2)).
T(n, m) = T'(n-1, m-1)+T'(n-1,m+1)+T'(n-1, m)+T'(n-2, m)+T'(n-3,m), where T'(n, m) = T(n, m)
for n >= 0 and 0< = m< = n and T'(n, m) = 0 otherwise.
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EXAMPLE
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Triangle begins
1,
1, 1,
3, 2, 1,
7, 7, 3, 1,
18, 20, 12, 4, 1,
48, 59, 40, 18, 5, 1,
132, 174, 132, 68, 25, 6, 1,
372, 517, 426, 247, 105, 33, 7, 1
We have, for instance, 132=59+18+40+12+3.
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CROSSREFS
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Sequence in context: A129689 A115990 A094531 this_sequence A111960 A130462 A059380
Adjacent sequences: A161006 A161007 A161008 this_sequence A161010 A161011 A161012
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KEYWORD
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easy,nonn,tabl
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Jun 02 2009
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