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A216853 18k^2-12k-7 interleaved with 18k^2+6k+5 for k>=0. 0

%I

%S -7,5,-1,29,41,89,119,185,233,317,383,485,569,689,791,929,1049,1205,

%T 1343,1517,1673,1865,2039,2249,2441,2669,2879,3125,3353,3617,3863,

%U 4145,4409,4709,4991,5309,5609,5945,6263,6617,6953,7325,7679,8069,8441,8849

%N 18k^2-12k-7 interleaved with 18k^2+6k+5 for k>=0.

%C The sequence (the third in the family) is present as a family of single interleaved sequence of which there are many which are separated or factored out to give individual sequences. The larger sequence produces two smaller interleaved sequences where one of them has the formulas above and the other interleaved sequence has the formulas (18n^2-24n-1) and (18n^2-6n+5). The latter interleaved sequence is A214493. There are three sequences in this family.

%H Eddie Gutierrez <a href="http://oddwheel.com/square_sequencesII.html"> New Interleaved Sequences Part B</a> on oddwheel.com, Section B1 Line No. 22 (square_sequencesII.html) Part B

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,-2,1).

%F G.f.: -(7-19*x+11*x^2-17*x^3)/((1+x)*(1-x)^3). - _Bruno Berselli_, Oct 05 2012

%F a(n) = (6*n*(3*n-4)-27*(-1)^n-1)/4. - _Bruno Berselli_, Oct 05 2012

%t Flatten[Table[{18 n^2 - 12 n - 7, 18 n^2 + 6 n + 5}, {n, 0, 22}]] (* _Bruno Berselli_, Oct 05 2012 *)

%o (MAGMA) &cat[[18*k^2-12*k-7, 18*k^2+6*k+5]: k in [0..22]]; // _Bruno Berselli_, Oct 05 2012

%o (PARI) vector(46, n, k=(n-1)\2; if(n%2, 18*k^2-12*k-7, 18*k^2+6*k+5)) \\ _Bruno Berselli_, Oct 05 2012

%Y Cf. A178218, A214345, A214393, A214405, A216876.

%K sign,easy

%O 0,1

%A _Eddie Gutierrez_, Sep 17 2012

%E Definition rewritten by _Bruno Berselli_, Oct 25 2012

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Last modified March 4 07:25 EST 2021. Contains 341781 sequences. (Running on oeis4.)