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A216876
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20k^2-20k-5 interleaved with 20k^2+5 for k=>0.
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7
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-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
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history;
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OFFSET
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0,1
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COMMENTS
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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.
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LINKS
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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).
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FORMULA
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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)
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MATHEMATICA
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Flatten[Table[{20*n^2 - 20*n - 5, 20*n^2 + 5}, {n, 0, 30}]] (* T. D. Noe, Sep 26 2012 *)
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PROG
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(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 */
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CROSSREFS
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Cf. A178218, A214345, A214493, A214393, A214405, A216871.
Sequence in context: A283711 A098526 A262122 * A019162 A024951 A092519
Adjacent sequences: A216873 A216874 A216875 * A216877 A216878 A216879
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KEYWORD
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sign,easy
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AUTHOR
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Eddie Gutierrez, Sep 18 2012
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EXTENSIONS
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More terms from T. D. Noe, Sep 26 2012
Definition rewritten by Bruno Berselli, Oct 25 2012
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STATUS
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approved
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