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A192874
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Constant term in the reduction by (x^2 -> x + 1) of the polynomial p(n,x) given in Comments.
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3
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1, 0, 4, 6, 26, 72, 246, 774, 2532, 8150, 26434, 85448, 276654, 895054, 2896788, 9373678, 30334682, 98163784, 317666758, 1027987894, 3326644036, 10765237670, 34837054674, 112735054856, 364818336766, 1180576879422
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OFFSET
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0,3
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COMMENTS
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The polynomial p(n,x) is defined by p(0,x) = 1, p(1,x) = x, and p(n,x) = x*p(n-1,x) + 2*(x^2)*p(n-1,x) + 1. See A192872.
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LINKS
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FORMULA
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a(n) = 2*a(n-1) + 6*a(n-2) - 5*a(n-3) - 6*a(n-4) + 4*a(n-5).
G.f.: (x^2-x+1)*(4*x^2+x-1) / ( (x-1)*(x^2-x-1)*(4*x^2+2*x-1) ). - R. J. Mathar, May 06 2014
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MATHEMATICA
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q = x^2; s = x + 1; z = 26;
p[0, x_] := 1; p[1, x_] := x;
p[n_, x_] := p[n - 1, x]*x + 2*p[n - 2, x]*x^2 + 1;
Table[Expand[p[n, x]], {n, 0, 7}]
reduce[{p1_, q_, s_, x_}] := FixedPoint[(s PolynomialQuotient @@ #1 + PolynomialRemainder @@ #1 &)[{#1, q, x}] &, p1]
t = Table[reduce[{p[n, x], q, s, x}], {n, 0, z}];
u1 = Table[Coefficient[Part[t, n], x, 0], {n, 1, z}] (* A192874 *)
u2 = Table[Coefficient[Part[t, n], x, 1], {n, 1, z}] (* A192875 *)
LinearRecurrence[{2, 6, -5, -6, 4}, {1, 0, 4, 6, 26}, 30] (* G. C. Greubel, Jan 08 2019 *)
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PROG
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(PARI) my(x='x+O('x^30)); Vec((x^2-x+1)*(4*x^2+x-1)/((x-1)*(x^2-x-1)*( 4*x^2+2*x-1))) \\ G. C. Greubel, Jan 08 2019
(Magma) I:=[1, 0, 4, 6, 26]; [n le 5 select I[n] else 2*Self(n-1)+6*Self(n-2) -5*Self(n-3)-6*Self(n-4)+4*Self(n-5): n in [1..30]]; // G. C. Greubel, Jan 08 2019
(Sage) ((x^2-x+1)*(4*x^2+x-1)/((x-1)*(x^2-x-1)*( 4*x^2+2*x-1))).series(x, 30).coefficients(x, sparse=False) # G. C. Greubel, Jan 08 2019
(GAP) a:=[1, 0, 4, 6, 26];; for n in [6..30] do a[n]:=2*a[n-1]+6*a[n-2] - 5*a[n-3]-6*a[n-4]+4*a[n-5]; od; a; # G. C. Greubel, Jan 08 2019
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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