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Search: id:A106511
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| A106511 |
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Expansion of (1+x)^2/((1+x+x^2)(1+x-x^2)). |
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+0
2
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| 1, 0, 0, 0, 1, -2, 3, -4, 6, -10, 17, -28, 45, -72, 116, -188, 305, -494, 799, -1292, 2090, -3382, 5473, -8856, 14329, -23184, 37512, -60696, 98209, -158906, 257115, -416020, 673134, -1089154, 1762289, -2851444, 4613733, -7465176, 12078908, -19544084, 31622993
(list; graph; listen)
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OFFSET
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0,6
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COMMENT
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Diagonal sums of the Riordan array ((1+x)/(1+x+x^2),x/(1+x)), A106509.
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FORMULA
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a(n)=sum{k=0..floor(n/2), sum{j=0..n-2k, (-1)^j*binomial(2n-3k-j, j)}}
(1/2) [(-1)^n*Fibonacci(n) + kronecker(-3,n) ]. - Ralf Stephan, Jun 2 2007
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CROSSREFS
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Cf. A024490.
Cf. A011646, A039834.
Adjacent sequences: A106508 A106509 A106510 this_sequence A106512 A106513 A106514
Sequence in context: A103599 A026502 A060163 this_sequence A024490 A056469 A004047
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KEYWORD
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easy,sign
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), May 04 2005
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