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A257181 Expansion of (1 - x) * (1 + x^4) / (1 + x^5) in powers of x. 1
1, -1, 0, 0, 1, -2, 1, 0, 0, -1, 2, -1, 0, 0, 1, -2, 1, 0, 0, -1, 2, -1, 0, 0, 1, -2, 1, 0, 0, -1, 2, -1, 0, 0, 1, -2, 1, 0, 0, -1, 2, -1, 0, 0, 1, -2, 1, 0, 0, -1, 2, -1, 0, 0, 1, -2, 1, 0, 0, -1, 2, -1, 0, 0, 1, -2, 1, 0, 0, -1, 2, -1, 0, 0, 1, -2, 1, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,6

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..2500

Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,-1).

FORMULA

Euler transform of length 10 sequence [-1, 0, 0, 1, -1, 0, 0, -1, 0, 1].

a(n) = a(-n) for all n in Z. a(n+5) = -a(n) unless n = 0 or -5. a(5*n) = 2 * (-1)^n unless n = 0. a(5*n + 2) = a(5*n + 3) = 0. a(5*n + 1) = a(5*n - 1) = -(-1)^n.

G.f.: (1 - x) * (1 + x^4) / (1 + x^5).

G.f.: (1 - x) * (1 - x^5) * (1 - x^8) / ((1 - x^4) * (1 - x^10)).

Convolution inverse is A257179.

a(n) = (-1)^floor( (n+4) / 5) * A164116(n).

EXAMPLE

G.f. = 1 - x + x^4 - 2*x^5 + x^6 - x^9 + 2*x^10 - x^11 + x^14 - 2*x^15 + ...

MATHEMATICA

a[ n_] := -Boole[n == 0] + {-1, 0, 0, 1, -2, 1, 0, 0, -1, 2}[[Mod[n, 10, 1]]];

a[ n_] := SeriesCoefficient[ (1 - x) * (1 + x^4) / (1 + x^5), {x, 0, Abs@n}];

CoefficientList[Series[(1-x)*(1+x^4)/(1+x^5), {x, 0, nmax}], x] (* G. C. Greubel, Aug 02 2018 *)

PROG

(PARI) {a(n) = if( n==0, 1, (-1)^(n\5) * [2, -1, 0, 0, 1][n%5 + 1])};

(PARI) {a(n) = polcoeff( (1 - x) * (1 + x^4) / (1 + x^5) + x * O(x^abs(n)), abs(n))};

(PARI) x='x+O('x^60); Vec((1-x)*(1+x^4)/(1+x^5)) \\ G. C. Greubel, Aug 02 2018

(MAGMA) m:=60; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!((1-x)*(1+x^4)/(1+x^5))); // G. C. Greubel, Aug 02 2018

CROSSREFS

Cf. A164116, A257179.

Sequence in context: A152815 A115296 A059048 * A164116 A164118 A180981

Adjacent sequences:  A257178 A257179 A257180 * A257182 A257183 A257184

KEYWORD

sign,easy

AUTHOR

Michael Somos, Apr 17 2015

STATUS

approved

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Last modified May 30 05:08 EDT 2020. Contains 334712 sequences. (Running on oeis4.)