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A137255
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a(n)=2a(n-1)+4a(n-2)-6a(n-3)-3a(n-4).
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1
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1, 2, 4, 8, 17, 36, 80, 178, 409, 942, 2212, 5204, 12377, 29472, 70592, 169198, 406801, 978426, 2357092, 5679488, 13696385, 33032892, 79703120, 192321034, 464168041, 1120302822, 2704242244, 6527724428, 15758096777, 38040729336, 91834772480
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| a(n)=(3/8)3^(n/2)*[1+(-1)^n]+(5/24)*3^((n+1)/2)*[1-(-1)^n]+(1/8)*[1+sqrt(2)]^(n+1)+(1/8)*[1-sqrt(2)]^(n+1). - Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 31 2008
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MAPLE
| a:=proc(n) options operator, arrow: expand((3/8)*3^((1/2)*n)*(1+(-1)^n)+(5/24)*3^((1/2)*n+1/2)*(1-(-1)^n)+(1/8)*(1+sqrt(2))^(n+1)+(1/8)*(1-sqrt(2))^(n+1)) end proc: seq(a(n), n=0..30); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 31 2008
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CROSSREFS
| Sequence in context: A002955 A202844 A093951 * A076892 A106462 A129987
Adjacent sequences: A137252 A137253 A137254 * A137256 A137257 A137258
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KEYWORD
| nonn
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AUTHOR
| Paul Curtz (bpcrtz(AT)free.fr), Mar 11 2008
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EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 31 2008
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