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A257196 Expansion of (1 + x) * (1 + x^5) / ((1 + x^2) * (1 + x^4)) in powers of x. 1
1, 1, -1, -1, 0, 1, 1, -1, 0, 1, -1, -1, 0, 1, 1, -1, 0, 1, -1, -1, 0, 1, 1, -1, 0, 1, -1, -1, 0, 1, 1, -1, 0, 1, -1, -1, 0, 1, 1, -1, 0, 1, -1, -1, 0, 1, 1, -1, 0, 1, -1, -1, 0, 1, 1, -1, 0, 1, -1, -1, 0, 1, 1, -1, 0, 1, -1, -1, 0, 1, 1, -1, 0, 1, -1, -1, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..76.

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

FORMULA

Euler transform of length 10 sequence [ 1, -2, 0, 0, 1, 0, 0, 1, 0, -1].

a(n) is multiplicative with a(2) = -1, a(2^e) = 0 if e>1, a(p^e) = 1 if p == 1 (mod 4), a(p^e) = (-1)^e if p == 3 (mod 4) and a(0) = 1.

G.f.: 1 + x / (1 + x^2) - x^2 / (1 + x^4).

G.f.: (1 + x) * (1 + x^5) / ((1 + x^2) * (1 + x^4)).

a(n) = -a(-n) for all n in Z unless n = 0. a(n+8) = a(n) unless n=0 or n=-8. a(4*n) = 0 unless n=0.

a(n) = A112299(n) unless n=0. - R. J. Mathar, Apr 19 2015

EXAMPLE

G.f. = 1 + x - x^2 - x^3 + x^5 + x^6 - x^7 + x^9 - x^10 - x^11 + x^13 + ...

MATHEMATICA

a[ n_] := Boole[n == 0] + {1, -1, -1, 0, 1, 1, -1, 0}[[Mod[ n, 8, 1]]];

a[ n_] := If[ n == 0, 1, Sign[ n] SeriesCoefficient[ (1 + x) * (1 + x^5) / ((1 + x^2) * (1 + x^4)), {x, 0, Abs @ n}]];

PROG

(PARI) {a(n) = (n==0) + [0, 1, -1, -1, 0, 1, 1, -1][n%8 + 1]};

(PARI) {a(n) = if( n==0, 1, n%2, (-1)^(n\2), n%4 == 2, -(-1)^(n\4), 0)};

(PARI) {a(n) = if( n==0, 1, sign(n) * polcoeff( (1 + x) * (1 + x^5) / ((1 + x^2) * (1 + x^4)) + x * O(x^abs(n)), abs(n)))};

CROSSREFS

Cf. A112299.

Sequence in context: A135839 A071022 A155076 * A176137 A120529 A099443

Adjacent sequences:  A257193 A257194 A257195 * A257197 A257198 A257199

KEYWORD

sign,mult,easy

AUTHOR

Michael Somos, Apr 17 2015

STATUS

approved

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Last modified February 25 03:33 EST 2018. Contains 299630 sequences. (Running on oeis4.)