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

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A216876 20k^2-20k-5 interleaved with 20k^2+5 for k=>0. 7
-5, 5, -5, 25, 35, 85, 115, 185, 235, 325, 395, 505, 595, 725, 835, 985, 1115, 1285, 1435, 1625, 1795, 2005, 2195, 2425, 2635, 2885, 3115, 3385, 3635, 3925, 4195, 4505, 4795, 5125, 5435, 5785, 6115, 6485, 6835, 7225, 7595, 8005, 8395, 8825, 9235, 9685 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

The sequence (the second in the family) is present as a family of single interleaved sequence of  which are separated or factored out of the larger sequence to give individual sequences. The larger sequence produces two smaller interleaved sequences where one of them  has the formula above and a first interleaved sequence. There are a total of two sequences in this family.

LINKS

Table of n, a(n) for n=0..45.

Eddie Gutierrez New Interleaved Sequences Part E on oddwheel.com, Section B1 Line No. 25 (square_sequencesV.html), Part E.

Index entries for linear recurrences with constant coefficients, signature (2,0,-2,1).

FORMULA

Contribution from Bruno Berselli, Sep 27 2012: (Start)

G.f.: -5*(1-3*x+3*x^2-5*x^3)/((1+x)*(1-x)^3).

a(n) = (5/2)*(2*n*(n-2)-3*(-1)^n+1).

a(n) = 5*A214345(n-3) with A214345(-3)=-1, A214345(-2)=1, A214345(-1)=-1. (End)

MATHEMATICA

Flatten[Table[{20*n^2 - 20*n - 5, 20*n^2 + 5}, {n, 0, 30}]] (* T. D. Noe, Sep 26 2012 *)

PROG

(MAGMA) &cat[[20*k^2-20*k-5, 20*k^2+5]: k in [0..22]]; // Bruno Berselli, Sep 27 2012

(PARI) vector(60, n, k=(n-1)\2; if(n%2, 20*k^2-20*k-5, 20*k^2+5)) \\ Charles R Greathouse IV, Sep 27 2012

(Maxima) A216876(n):=(5/2)*(2*n*(n-2)-3*(-1)^n+1)$

makelist(A216876(n), n, 0, 30); /* Martin Ettl, Nov 01 2012 */

CROSSREFS

Cf. A178218, A214345, A214493, A214393, A214405, A216871.

Sequence in context: A283711 A098526 A262122 * A019162 A024951 A092519

Adjacent sequences:  A216873 A216874 A216875 * A216877 A216878 A216879

KEYWORD

sign,easy

AUTHOR

Eddie Gutierrez, Sep 18 2012

EXTENSIONS

More terms from T. D. Noe, Sep 26 2012

Definition rewritten by Bruno Berselli, Oct 25 2012

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 9 00:32 EST 2019. Contains 329871 sequences. (Running on oeis4.)