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URL: https://oeis.org/A114014

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A114014
Expansion of g.f. (1 + 2*x)^4/((1 + x)*(1 - 16*x^2)).
1
1, 7, 33, 127, 529, 2031, 8465, 32495, 135441, 519919, 2167057, 8318703, 34672913, 133099247, 554766609, 2129587951, 8876265745, 34073407215, 142020251921, 545174515439, 2272324030737, 8722792247023, 36357184491793
OFFSET
0,2
FORMULA
G.f.: (-1)*(x + 1/2)^4/((x - 1/4)*(x + 1/4)*(x + 1)).
From Colin Barker, Dec 03 2012: (Start)
a(n) = (5*(-4)^n - 8*(-1)^n + 243*4^n)/120 for n>1.
G.f.: (1 +8*x +24*x^2 +32*x^3 +16*x^4)/((1+x)*(1-4*x)*(1+4*x)). (End)
From G. C. Greubel, Jul 07 2021: (Start)
a(n) = 4*a(n-1) + (-1)^n*(4^(n-1) -1)/3, n>2, with a(0) = 1, a(1) = 7, and a(2) = 33.
E.g.f.: (1/120)(243*exp(4*x) + 5*exp(-4*x) - 8*exp(-x) - 120*(1 + x)). (End)
MATHEMATICA
CoefficientList[Series[(1+2*x)^4/((1+x)*(1-16*x^2)), {x, 0, 40}], x]
a[n_]:= a[n]= If[n<2, 7^n, If[n==2, 33, 4*a[n-1] +(-1)^n*(4^(n-1) -1)/3]];
Table[a[n], {n, 0, 40}] (* G. C. Greubel, Jul 07 2021 *)
LinearRecurrence[{-1, 16, 16}, {1, 7, 33, 127, 529}, 30] (* Harvey P. Dale, Aug 07 2023 *)
PROG
(Magma) [1, 7] cat [(1/30)*(4^(n-1)*(243 + 5*(-1)^n) - 2*(-1)^n): n in [2..40]]; // G. C. Greubel, Jul 07 2021
(SageMath) [1, 7]+[(1/30)*(4^(n-1)*(243 + 5*(-1)^n) - 2*(-1)^n) for n in (2..40)] # G. C. Greubel, Jul 07 2021
CROSSREFS
Cf. A112627.
Sequence in context: A000605 A215054 A350643 * A375549 A229515 A320907
KEYWORD
nonn,easy
AUTHOR
Roger L. Bagula, Jan 31 2006
EXTENSIONS
New name and edited by G. C. Greubel, Jul 07 2021
STATUS
approved