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Search: id:A077946
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| A077946 |
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Expansion of 1/(1-x-2*x^2-2*x^3). |
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+0
2
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| 1, 1, 3, 7, 15, 35, 79, 179, 407, 923, 2095, 4755, 10791, 24491, 55583, 126147, 286295, 649755, 1474639, 3346739, 7595527, 17238283, 39122815, 88790435, 201512631, 457339131, 1037945263, 2355648787, 5346217575, 12133405675, 27537138399, 62496384899, 141837473047
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OFFSET
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0,3
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FORMULA
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a(n) = leftmost term in M^n * [1 0 0], where M = the 3X3 matrix [1 1 1 / 2 0 0 / 0 1 0]. a(n) = a(n-1) + 2*a(n-2) + 2*a(n-3). a(n)/a(n-1) tends to 2.26953084..., an eigenvalue of M and a root of the characteristic polynomial x^3 - x^2 - 2x - 2. a(6) = 79 = 35 + 2*15 + 2*7 = a(5) + 2*a(4) + 2*a(3). - Gary W. Adamson (qntmpkt(AT)yahoo.com), Dec 21 2004
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CROSSREFS
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Cf. A077970.
Sequence in context: A140498 A136029 A101892 this_sequence A077970 A124696 A081669
Adjacent sequences: A077943 A077944 A077945 this_sequence A077947 A077948 A077949
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KEYWORD
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nonn
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AUTHOR
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njas, Nov 17 2002
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