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A123189
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a(1)=1; a(2)=1; a(3)=6; a(n)=3a(n-1)+3a(n-2)-4a(n-3) for n >=4.
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0
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1, 1, 6, 17, 65, 222, 793, 2785, 9846, 34721, 122561, 432462, 1526185, 5385697, 19005798, 67069745, 236683841, 835237566, 2947485241, 10401433057, 36705804630, 129531772097, 457106997953, 1613093091630, 5692473180361
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OFFSET
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1,3
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LINKS
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Table of n, a(n) for n=1..25.
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MAPLE
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a[1]:=1: a[2]:=1: a[3]:=6: for n from 4 to 25 do a[n]:=3*a[n-1]+3*a[n-2]-4*a[n-3] od: seq(a[n], n=1..25);
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MATHEMATICA
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M = {{1, -2, 1}, {-2, 2, 0}, {1, 1, 0}} v[1] = {1, 0, 0} v[n_] := v[n] = M.v[n - 1]; a1 = Table[v[n][[1]], {n, 1, 50}]
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CROSSREFS
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Sequence in context: A151350 A195741 A006758 * A219847 A047156 A219294
Adjacent sequences: A123186 A123187 A123188 * A123190 A123191 A123192
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KEYWORD
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nonn
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AUTHOR
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Roger Bagula, Oct 03 2006
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EXTENSIONS
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Edited by N. J. A. Sloane, Oct 08 2006
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STATUS
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approved
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