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A176971 Expansion of (1+x)/(1+x-x^3) in powers of x. 4
1, 0, 0, 1, -1, 1, 0, -1, 2, -2, 1, 1, -3, 4, -3, 0, 4, -7, 7, -3, -4, 11, -14, 10, 1, -15, 25, -24, 9, 16, -40, 49, -33, -7, 56, -89, 82, -26, -63, 145, -171, 108, 37, -208, 316, -279, 71, 245, -524, 595 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,9

COMMENTS

Except for signs the sequence is the essentially same as A078013, A050935 and A104769.

LINKS

Table of n, a(n) for n=0..49.

Index to sequences with linear recurrences with constant coefficients, signature (-1,0,1). [From R. J. Mathar, Apr 30 2010]

FORMULA

a(n) = A000931(n)^2 -A000931(n-1)*A000931(n+1).

a(n) = -a(n-1) +a(n-3). [From R. J. Mathar, Apr 30 2010]

a(n) = -A104769(n) - A104769(n+1). - Ralf Stephan, Aug 18 2013

G.f.: 1 / (1 - x^3 / (1 + x)). - Michael Somos, Dec 13 2013

a(n) = A182097(-n). - Michael Somos, Dec 13 2013

A000931(n) = a(n)^2 - a(n-1) * a(n+1). - Michael Somos, Dec 13 2013

BINOMIAL transform is A005251(n+1). - Michael Somos, Dec 13 2013

EXAMPLE

G.f. = 1 + x^3 - x^4 + x^5 - x^7 + 2*x^8 - 2*x^9 + x^10 + x^11 - 3*x^12 + ...

MATHEMATICA

a[0] := 1; a[1] = 0; a[2] = 0;

a[n_] := a[n] = a[n - 2] + a[n - 3];

b = Table[a[n], {n, 0, 50}];

Table[b[[n]]^2 - b[[n - 1]]*b[[n + 1]], {n, 1, Length[b] - 1}]

a[ n_] := If[ n >= 0, SeriesCoefficient[ (1 + x) / (1 + x - x^3), {x, 0, n}], SeriesCoefficient[ 1 / (1 - x^2 - x^3), {x, 0, Abs@n}]] (* Michael Somos, Dec 13 2013 *)

PROG

(PARI) {a(n) = if( n>=0, polcoeff( (1 + x) / (1 + x - x^3) + x * O(x^n), n), polcoeff( 1 / (1 - x^2 - x^3) + x * O(x^-n), -n))} /* Michael Somos, Dec 13 2013 */

CROSSREFS

Cf. A000931, A005251, A104769, A182097.

Sequence in context: A036064 A090706 A228371 * A247917 A050935 A104769

Adjacent sequences:  A176968 A176969 A176970 * A176972 A176973 A176974

KEYWORD

sign,easy

AUTHOR

Roger L. Bagula, Apr 29 2010

STATUS

approved

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Last modified December 22 16:49 EST 2014. Contains 252364 sequences.