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A129997
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a(n) = 4*a(n-1) + (n-6)*a(n-2).
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0
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0, 1, 4, 14, 52, 208, 884, 3952, 18460, 89648, 450892, 2341456, 12522068, 68819920, 387978292, 2240112368, 13228210684, 79794191152, 491143503500, 3081692690128, 19693923313012, 128082776294096, 847127801497588
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OFFSET
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1,3
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LINKS
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FORMULA
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a(n) ~ 26*sqrt(2)*exp(4*sqrt(n)-n/2-4)*n^(n/2-5/2)*(1-19/(3*sqrt(n))+1/(6*n)) . - Vaclav Kotesovec, Oct 20 2012
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MATHEMATICA
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M[n_] := {{0, 1}, {-4 + n, 4}} v[0] = {0, 1}; v[n_] := v[n] = M[n].v[m - 1] a = Table[v[m][[1]], {m, 0, 30}]
RecurrenceTable[{a[n] == 4*a[n-1] + (n-6)*a[n-2], a[1]==0, a[2]==1}, a, {n, 20}] (* Vaclav Kotesovec, Oct 20 2012 *)
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PROG
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(Magma) [n le 2 select n-1 else 4*Self(n-1)+(n-6)*Self(n-2): n in [1..30]]; // Vincenzo Librandi, May 24 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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