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

 

Logo

"Email this user" was broken Aug 14 to 9am Aug 16. If you sent someone a message in this period, please send it again.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A112299 Expansion of x * (1 - x) * (1 - x^2) * (1 - x^3) / (1 - x^8) in powers of x. 2
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, 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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Periodic with period length 8.

Sum_{k>=1} a(k)/k = Pi/8. - Jaume Oliver Lafont, Oct 20 2009

LINKS

Table of n, a(n) for n=1..105.

M. Somos, Rational Function Multiplicative Coefficients

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

FORMULA

Euler transform of length 8 sequence [ -1, -1, -1, 0, 0, 0, 0, 1].

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).

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

G.f.: f(x) - f(x^2) where f(x) := x / (1 + x^2). - Michael Somos, Jun 19 2015

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

a(2*n) = - A056594(n-1). a(2*n + 1) = A033999(n). a(4*n + 1) = 1. a(4*n + 3) = -1. a(4*n + 2) = - A033999(n). - Michael Somos, Jun 19 2015

a(n) = A257196(n) unless n=0. - Michael Somos, Sep 01 2015

EXAMPLE

G.f. = x - x^2 - x^3 + x^5 + x^6 - x^7 + x^9 - x^10 - x^11 + x^13 + x^14 - x^15 + ...

MATHEMATICA

LinearRecurrence[{0, -1, 0, -1, 0, -1}, {1, -1, -1, 0, 1, 1}, 110] (* Harvey P. Dale, Dec 07 2014 *)

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

PROG

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

(PARI) {a(n) = [ 0, 1, -(-1)^(n\4), -1][n%4 + 1]}; /* Michael Somos, Jun 19 2015 */

CROSSREFS

Cf. A033999, A056594, A257196.

Sequence in context: A132350 A076213 A120525 * A014677 A175087 A127872

Adjacent sequences:  A112296 A112297 A112298 * A112300 A112301 A112302

KEYWORD

sign,mult,easy

AUTHOR

Michael Somos, Sep 02 2005

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 17 07:13 EDT 2017. Contains 290635 sequences.