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