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 A216875 20k^2-40k+10 interleaved with 20k^2-20k+10 for k>=0. 2
 10, 10, -10, 10, 10, 50, 70, 130, 170, 250, 310, 410, 490, 610, 710, 850, 970, 1130, 1270, 1450, 1610, 1810, 1990, 2210, 2410, 2650, 2870, 3130, 3370, 3650, 3910, 4210, 4490, 4810, 5110, 5450, 5770, 6130, 6470, 6850, 7210, 7610, 7990, 8410, 8810, 9250, 9670 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS The sequence (the first 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 second 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.: 10*(1-x-3*x^2+5*x^3)/((1+x)*(1-x)^3). a(n) = (5/2)*(2*n*(n-4)-3*(-1)^n+7). a(n) = 10*A178218(n-3) with A178218(-3)=1, A178218(-2)=1, A178218(-1)=-1, A178218(0)=1. (End) MATHEMATICA Flatten[Table[{20 n^2 - 40 n + 10, 20 n^2 - 20 n + 10}, {n, 0, 23}]] (* Bruno Berselli, Sep 27 2012 *) LinearRecurrence[{2, 0, -2, 1}, {10, 10, -10, 10}, 60] (* Harvey P. Dale, Sep 18 2020 *) PROG (MAGMA) &cat[[20*k^2-40*k+10, 20*k^2-20*k+10]: k in [0..23]]; // Bruno Berselli, Sep 27 2012 (PARI) vector(47, n, k=(n-1)\2; if(n%2, 20*k^2-40*k+10, 20*k^2-20*k+10)) \\ Bruno Berselli, Sep 28 2012 CROSSREFS Sequence in context: A245403 A091837 A316650 * A166710 A211872 A178166 Adjacent sequences:  A216872 A216873 A216874 * A216876 A216877 A216878 KEYWORD sign,easy AUTHOR Eddie Gutierrez, Sep 18 2012 EXTENSIONS Definition rewritten by Bruno Berselli, Oct 25 2012 STATUS approved

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Last modified May 11 12:47 EDT 2021. Contains 343791 sequences. (Running on oeis4.)