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A121801 Expansion of 2*x^2*(3-x)/((1+x)*(x^2-3*x+1)) . 4
0, 6, 10, 32, 78, 210, 544, 1430, 3738, 9792, 25630, 67106, 175680, 459942, 1204138, 3152480, 8253294, 21607410, 56568928, 148099382, 387729210, 1015088256, 2657535550, 6957518402, 18215019648, 47687540550, 124847601994 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

FORMULA

a(n) = 2*a(n-1)+2*a(n-2)-a(n-3).

a(n) = -2*A121646(n+1).

MATHEMATICA

c[i_, k_] := Floor[Mod[i/2^k, 2]] b[i_, k_] := If[c[i, k] == 0 && c[ i, k + 1] == 0, 0, If[c[i, k] == 1 && c[i, k + 1] == 1, 0, 1]] n = 4 - 1; M = Table[If[Sum[b[i, k]*b[j, k], {k, 0, n}] == 0, 1, 0], {j, 0, n}, {i, 0, n}] v[1] = {0, 1, 2, 3} v[n_] := v[n] = M.v[n - 1] a = Table[Floor[v[n][[1]]], {n, 1, 50}] Det[M - x*IdentityMatrix[4]] Factor[%] aaa = Table[x /. NSolve[Det[M - x*IdentityMatrix[4]] == 0, x][[n]], {n, 1, 4}] Abs[aaa] a1 = Table[N[a[[n]]/a[[n - 1]]], {n, 7, 50}]

CROSSREFS

Sequence in context: A130440 A178676 A137272 * A192774 A032740 A167330

Adjacent sequences:  A121798 A121799 A121800 * A121802 A121803 A121804

KEYWORD

nonn

AUTHOR

Roger Bagula and Gary Adamson (rlbagulatftn(AT)yahoo.com), Aug 27 2006

EXTENSIONS

Edited by the Associate Editors of the OEIS, Aug 18 2009

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Last modified February 13 22:36 EST 2012. Contains 205567 sequences.