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A116404
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Expansion of (1-x)/((1-x)^2-x^2(1+x)^2).
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3
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1, 1, 2, 6, 15, 35, 84, 204, 493, 1189, 2870, 6930, 16731, 40391, 97512, 235416, 568345, 1372105, 3312554, 7997214, 19306983, 46611179, 112529340, 271669860, 655869061, 1583407981, 3822685022, 9228778026, 22280241075, 53789260175
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| Diagonal sums of number triangle A114123. Binomial transform of A114122. Congruent to 1,1,0,0,1,1,... modulo 2.
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (2,0,2,1).
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FORMULA
| G.f.: (1-x)/(1-2x-2x^3-x^4); a(n)=2a(n-1)+2a(n-3)+a(n-4); a(n)=sum{k=0..floor(n/2), sum{j=0..n-k, C(2k,n-2k-j)*C(n-2k,j)*2^(n-2k-j)}}.
2*a(n) = A056594(n) +A000129(n+1). - R. J. Mathar, Oct 25 2011
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CROSSREFS
| Sequence in context: A090982 A153517 A136302 * A084860 A084798 A017923
Adjacent sequences: A116401 A116402 A116403 * A116405 A116406 A116407
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Feb 07 2006
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