login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A175722 a(n) = -a(n-1) + a(n-2) - F(-n) + 1, a(0) = 1, a(1) = -1, where F() = Fibonacci numbers A000045. 4
1, -1, 4, -6, 14, -24, 47, -83, 152, -268, 476, -832, 1453, -2517, 4348, -7474, 12810, -21880, 37275, -63335, 107376, -181656, 306744, -517056, 870169, -1462249, 2453812, -4112478, 6884102, -11510808, 19226951, -32084027, 53489288, -89097892, 148290068 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

FORMULA

Expansion of 1/(- x^m + 1 - x^(1 + m) + x + 3 x^(2 + m) - 2* x^2 - x^(3 + m)) for m=2.

G.f.: 1 / ((1 - x) * (1 + x - x^2)^2). - Michael Somos, Mar 11 2014

a(n) = A006478(-2-n) for all n in Z. - Michael Somos, Mar 11 2014

EXAMPLE

G.f. = 1 - x + 4*x^2 - 6*x^3 + 14*x^4 - 24*x^5 + 47*x^6 - 83*x^7 + 152*x^8 + ...

MATHEMATICA

f[x_, m_] = ExpandAll[(x - x^(m + 1))*(1 - x - x^2) - (1 - 2*x + x^(m + 1))];

g[x_, n_] = ExpandAll[x^(m + 3)*f[1/x, m]];

a = Table[Table[SeriesCoefficient[

      Series[1/g[x, m], {x, 0, 20}], n], {n, 0, 20}], {m, 1, 20}]

CoefficientList[Series[1/((1 - x) (1 + x - x^2)^2), {x, 0, 50}], x] (* Vincenzo Librandi, Mar 13 2014 *)

RecurrenceTable[{a[0]==1, a[1]==-1, a[n]==-a[n-1]+a[n-2]-Fibonacci[-n]+1}, a, {n, 40}] (* Harvey P. Dale, May 12 2018 *)

PROG

(PARI) {a(n) = if( n<0, polcoeff( x^5 / ((1 - x) * (1 - x - x^2)^2) + x * O(x^-n), -n), polcoeff( 1 / ((1 - x) * (1 + x - x^2)^2) + x * O(x^n), n))}; /* Michael Somos, Mar 11 2014 */

(MAGMA) m:=50; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/((1-x)*(1+x-x^2)^2))); // G. C. Greubel, Aug 14 2018

CROSSREFS

Cf. m=1: A077899, m large: A077925.

Cf. A006478.

Sequence in context: A097271 A126867 A027632 * A200186 A192782 A188576

Adjacent sequences:  A175719 A175720 A175721 * A175723 A175724 A175725

KEYWORD

sign,easy,changed

AUTHOR

Roger L. Bagula, Dec 04 2010

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 20 13:30 EDT 2018. Contains 313917 sequences. (Running on oeis4.)