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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 (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 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

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Last modified June 5 18:48 EDT 2020. Contains 334854 sequences. (Running on oeis4.)