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Search: id:A077949
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| A077949 |
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Expansion of 1/(1-x-2*x^3). |
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+0
6
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| 1, 1, 1, 3, 5, 7, 13, 23, 37, 63, 109, 183, 309, 527, 893, 1511, 2565, 4351, 7373, 12503, 21205, 35951, 60957, 103367, 175269, 297183, 503917, 854455, 1448821, 2456655, 4165565, 7063207, 11976517, 20307647, 34434061, 58387095, 99002389, 167870511, 284644701
(list; graph; listen)
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OFFSET
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0,4
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COMMENT
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Row sums of the Riordan array (1, x(1+2x^2)); - Paul Barry (pbarry(AT)wit.ie), Jan 12 2006
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FORMULA
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a(n)=sum{k=0..floor(n/2), C(n-2k, k)2^k} - Paul Barry (pbarry(AT)wit.ie), Nov 18 2003
a(n)=sum{k=0..n, C(k, floor((n-k)/2))2^((n-k)/2)(1+(-1)^(n-k))/2}; - Paul Barry (pbarry(AT)wit.ie), Jan 12 2006
a(n) = term (1,1) in the 3x3 matrix [1,1,0; 0,0,1; 2,0,0]^n. [From Alois P. Heinz (heinz(AT)hs-heilbronn.de), Aug 16 2008]
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MAPLE
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a := n -> (Matrix([[1, 1, 0], [0, 0, 1], [2, 0, 0]])^n)[1, 1]; seq (a(n), n=0..38); [From Alois P. Heinz (heinz(AT)hs-heilbronn.de), Aug 16 2008]
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CROSSREFS
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Unsigned version of A077974. Cf. A003229.
Sequence in context: A125272 A127443 A003229 this_sequence A077974 A126273 A007658
Adjacent sequences: A077946 A077947 A077948 this_sequence A077950 A077951 A077952
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KEYWORD
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nonn,new
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AUTHOR
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njas, Nov 17 2002
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