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A103143
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a(n)=a(n-1)+a(n-2)+3a(n-3).
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1
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0, 0, 1, 1, 2, 6, 11, 23, 52, 108, 229, 493, 1046, 2226, 4751, 10115, 21544, 45912, 97801, 208345, 443882, 945630, 2014547, 4291823, 9143260, 19478724, 41497453, 88405957, 188339582, 401237898, 854795351, 1821051995, 3879561040, 8264999088, 17607716113
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,5
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COMMENTS
| Diagonal sums of the Pascal-(1,3,1) triangle A081578.
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FORMULA
| G.f.: 1/(1-x-x^2-3x^3)
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MATHEMATICA
| LinearRecurrence[{1, 1, 3}, {0, 0, 1}, 50] (* From Vladimir Joseph Stephan Orlovsky, May 25 2011 *)
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CROSSREFS
| Cf. A077947.
Sequence in context: A005999 A102429 A080012 * A005673 A084308 A067605
Adjacent sequences: A103140 A103141 A103142 * A103144 A103145 A103146
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Jan 24 2005
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