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Search: id:A077948
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| A077948 |
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Expansion of 1/(1-x-x^2+2*x^3). |
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+0
5
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| 1, 1, 2, 1, 1, -2, -3, -7, -6, -7, 1, 6, 21, 25, 34, 17, 1, -50, -83, -135, -118, -87, 65, 214, 453, 537, 562, 193, -319, -1250, -1955, -2567, -2022, -679, 2433, 5798, 9589, 10521, 8514, -143, -12671, -29842, -42227, -46727, -29270, 8457, 72641, 139638, 195365, 189721, 105810, -95199, -368831
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Row sums of Riordan array (1/(1-x^2), x(1-2x^2)/(1-x^2)), A117355. - Paul Barry (pbarry(AT)wit.ie), Mar 09 2006
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FORMULA
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a(n)=sum{k=0..n, sum{j=0..n-k, C(j-(n-k)/2-1,j)C(k,j)(1+(-1)^(n-k))/2}}; - Paul Barry (pbarry(AT)wit.ie), Mar 09 2006
a(n)=a(n-1)+a(n-2)-2a(n-3). If defined by this recurrence, the sequence could be preceded by 0, 0. - Paul Curtz (bpcrtz(AT)free.fr), Feb 17 2008
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CROSSREFS
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Cf. A077971.
Sequence in context: A130030 A088022 A016732 this_sequence A077971 A030018 A010739
Adjacent sequences: A077945 A077946 A077947 this_sequence A077949 A077950 A077951
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KEYWORD
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sign
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Nov 17 2002
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