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A216875 20k^2-40k+10 interleaved with 20k^2-20k+10 for k>=0.

%I A216875 #30 Sep 08 2022 08:46:03
%S A216875 10,10,-10,10,10,50,70,130,170,250,310,410,490,610,710,850,970,1130,
%T A216875 1270,1450,1610,1810,1990,2210,2410,2650,2870,3130,3370,3650,3910,
%U A216875 4210,4490,4810,5110,5450,5770,6130,6470,6850,7210,7610,7990,8410,8810,9250,9670
%N A216875 20k^2-40k+10 interleaved with 20k^2-20k+10 for k>=0.
%C A216875 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.
%H A216875 Eddie Gutierrez <a href="http://www.oddwheel.com/square_sequencesV.html">New Interleaved Sequences Part E</a> on oddwheel.com  Section B1 Line No. 25 (square_sequencesV.html) Part E.
%H A216875 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,-2,1).
%F A216875 Contribution from _Bruno Berselli_, Sep 27 2012: (Start)
%F A216875 G.f.: 10*(1-x-3*x^2+5*x^3)/((1+x)*(1-x)^3).
%F A216875 a(n) = (5/2)*(2*n*(n-4)-3*(-1)^n+7).
%F A216875 a(n) = 10*A178218(n-3) with A178218(-3)=1, A178218(-2)=1, A178218(-1)=-1, A178218(0)=1. (End)
%t A216875 Flatten[Table[{20 n^2 - 40 n + 10, 20 n^2 - 20 n + 10}, {n, 0, 23}]] (* _Bruno Berselli_, Sep 27 2012 *)
%t A216875 LinearRecurrence[{2,0,-2,1},{10,10,-10,10},60] (* _Harvey P. Dale_, Sep 18 2020 *)
%o A216875 (Magma) &cat[[20*k^2-40*k+10, 20*k^2-20*k+10]: k in [0..23]]; // _Bruno Berselli_, Sep 27 2012
%o A216875 (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
%K A216875 sign,easy
%O A216875 0,1
%A A216875 _Eddie Gutierrez_, Sep 18 2012
%E A216875 Definition rewritten by _Bruno Berselli_, Oct 25 2012