A091096 Expansion of (1+5x-40x^2)/((1-5x)(1+5x)).

1, 5, -15, 125, -375, 3125, -9375, 78125, -234375, 1953125, -5859375, 48828125, -146484375, 1220703125, -3662109375, 30517578125, -91552734375, 762939453125, -2288818359375, 19073486328125, -57220458984375, 476837158203125, -1430511474609375

Offset

0,2

Comments

a(0)=1, a(2n-1)=k^(2n-1), a(2n)=(2-k)k^(2n-1), k=5; G.f.: (1+kx+(2-2k)kx^2)/((1-kx)(1+kx)), k=5.

Links

Table of n, a(n) for n=0..22.

Index entries for linear recurrences with constant coefficients, signature (0,25).

Formula

a(n)=5^n/5 +(-4)(-5)^n/5+8*0^n/5

Mathematica

CoefficientList[Series[(1+5x-40x^2)/((1-5x)(1+5x)), {x, 0, 30}], x] (* or *) LinearRecurrence[{0, 25}, {1, 5, -15}, 30] (* Harvey P. Dale, Dec 26 2015 *)

Crossrefs

Sequence in context: A173736 A244298 A050542 * A116957 A124209 A207970

Adjacent sequences: A091093 A091094 A091095 * A091097 A091098 A091099

Keyword

easy,sign

Author

Paul Barry, Dec 19 2003

Status

approved